Let me just be totally honest with you:
I would
love to help you develop this cube,
but you have got to figure out what you want out of it first!
For reference: you made this thread looking to cut to 405 from 455ish+; you're now down to 321 (as of this posting) and looking to plug holes! I know (as does everyone else here) how crazy the cube-making process can be, but you have to have some direction. "If you don't stand for something, you will fall for anything." You will get your best help here asking clear questions and giving us clear ideas of what you want. We all think we're really clever and have a lot of ideas that are pretty convincing, but if you don't know what you want coming into this, you're going to be pulled into a muddy format that is cool, but not quite awesome.
Some thoughts that jump out at me:
Allied guilds:
WU: Fish style aggro/Some form of tap out control
UB: Classic slow control (counter/kill everything, draw cards, win with bomb)/Mill
BR: Aggro with sacrifice theme
RG: Big aggro/Fires of Yavimaya/Ramp into monsters
GW: Ramp/Tokens/Anthems
Enemy guilds:
WB: Humans fish style aggro/Mill and Wrath control
BG: Graveyard/Dredge/Constellation
GU: Threshold effects/Flashback
UR: Spells matter/Prowess triggers
RW: Aggro/Tokens
This is an alright starting direction, but you need to define the finer lines. How does "tap-out control" differ from "slow control" or "mill and wrath control"? Further: why put mill in WB, when UB is typically the mill pairing? For UG: What "Threshold effects" are you looking to use? Are any of them any good? How weak will your environ have to be for Threshold to be a mechanic you can justify using?
What I would suggest, if you're really committed to building this cube up right and making a format you LOVE, is to go through and find key cards you like and cards that look cool to build around, and collect them together. ie, "Here are 8 white cards I love, and here are 2 W/B cards I'd like to pair together and see if I could build into a theme, and I really like these 3 B/G cards, so I want them to be viable..." One of the hardest parts of building a good environ is actually accepting that the concept will not generate the desired execution unless you work at it very hard.
An example from my own experience: As much as I love, love, love the design of
Wydwen, the Biting Gale, I did not craft a format that was friendly to her, and so she never really got played. It made me sad, but she had to be cut - the concept ("wow, cool, a hard-to-kill UB control finisher that looks super rad!") did not fit the pair's general execution ("UB usually wants to be a controlling midrange deck that builds up value early and centers the mid-game around key disruptive plays and hard hits. This card just isn't doing anything for that style of play, is it? Darn. Cutting time.").
So, consider this angle going forward: isolate the cards you LOVE (for me, that's spicy nostalgia pieces like
Quirion Dryad and
Emeria Angel) and craft an environ that can allow them to be playable and fun.
To address some of your questions... (numbered for my convenience)
The things I want to try out that spring to mind are:
1. I want milling to be a way to win, but I'm not sure how to make it fair or fun. Enchantments like
Sphinx's Tutelage and
Curse of the Bloody Tome?
Real talk: mill is rarely "fair or fun" unless your play group believes it to be "fair and fun". For mill over here, I have
Dakra Mystic,
Hedron Crab,
Mindshrieker,
Jace Beleren,
Talent of the Telepath,
Nightveil Specter,
Lantern of Insight,
Codex Shredder,
Altar of Dementia,
Mesmeric Orb,
Ashiok, Nightmare Weaver, and
Oona, Queen of the Fae. I also have a ULD and
Nephalia Drownyard is in there, naturally. The deck can come together pretty well even with just a few of the pieces for us; one memorable game in particular led to me ultimating
Garruk Wildspeaker and sacrificing a
Kitchen Finks and a bunch of buffed tokens from an
Awakening Zone to
Altar of Dementia for the win when my opponent was going to finish me off the following turn. That said, many of these tools are things some playgroups will be unhappy about. Personally, we are amused by mill, but note that it's a very playgroup-dependent style of play.
2. I want to see some reanimation and flashback spells and threshold to fight against good mill strategies.
I think in general Threshold is outclassed; what cards specifically were you thinking of? At any rate, planting a sub-theme in your cube as a "mill punisher" isn't really necessary, because mill is hard to make work as it is, and as such, it's not a deck you'll see super often, or need to plan against by planting cards that make mill's already-hard-win-con even harder. I do love flashback spells for their immense value added over regular cards, but you don't need to think of them as a mill responder.
3. I want to have enough ETB triggers to make
Ninja of the Deep Hours and
Birthing Pod fun and competitive.
I think that, fundamentally, Ninja only works in really low-powered environs, and I've never been excited enough about
Birthing Pod in my own very fast, interactive format to want to try it out, so I can't give you much advice here.
4. I am happy with the removal being toned down to match the threats. I'm happy with white having enchantment and return to library removal along side instant speed token spells. I'm fine with black removal being BB or sorcery speed for the most part.
How does this notion of instant-speed white removal map with your prior expressed desired for "tap-out control"? Regardless of that: why make black stick to mostly sorcery speed and hard-to-cast spells if white is going to get instant speed? I think this balance can work, for sure, but you have to be careful, and I think you need to really dwell on white, black, red, and blue answers carefully to make a good format. Remember that spells that have two (or more!) mana symbols in them are very limiting in deckbuilding; making most of black's removal
just means that your decks that go black will often be forced to be mostly mono-black with splashes, limiting the diversity of your format drastically.
5. How do I balance that with my strong desire to see aggro decks be worth drafting? I hate seeing everyone try to draft midrange value decks. (And here I am wanting Birthing Pod to take up three spots. Lol.)
imho aggro is hard to make worth drafting because it isn't as "exciting" as midrange value beasts. So, to bait players into aggro, you need to monitor your Wall-style creatures and your life gain very carefully, and avoid huge value swings like
Thragtusk if you can. Aggro needs to be able to be a rewarding playstyle that can transition into the early-midgame without too much pain; things that dump value on the board like
Thragtusk or
Wall of Omens will drastically impede aggro's viability. That said, plentiful removal is good for aggro, too - they like clearing a path!
6. Could
Wildfire be a viable strategy for Rx decks without ruining the format with mana artifacts?
Wildfire never worked over here even running two copies and gallons of stones. I love the deck, and it's great fun in bullshitty powermax cubes, but it was never happening over here, so I can't give you any better advice here other than: you will really
need mana stones to ever make it worth drafting, and if you're trying to avoid the stones, know that
Wildfire will probably not work.
7. I really want to use
Pia and Kiran Nalaar in some way.
Do so! It's not a hard card to throw in.
8. I'm interested in prowess as a theme for URW. Maybe there is overlap with tokens and flashback and enchantments as removal?
Well, naturally - the more noncreature spells, the better for Prowess. It's not something that needs any more push than cheap noncreature effects, though, imo.
I feel like maybe I want to do too many things. Can each guild support two styles of deck? Is there enough overlap?
My opinion on each guild running multiple themes is a firm
no. Some guilds are friendly to multiple styles, for sure, but most are not; they will either be rather generic decks that do a function in a unique way (ie aggro, midrange, control), or they will be thematically linked decks that can pursue a built-in angle that is uniquely cool to them (ie UG super-ramp, BR lockout, GW lands-matter, WB attrition, GR +1/+1 counters, etc). Packing in multiple themes for each guild can get messy - focus on one each, and look for overlaps for now. I
still don't have an explicit WR theme, so don't stress about it; instead just enjoy the natural lovemaking those odd pairs create (WR control is gorgeoussss) and hope that they bear out a specific idea later (for the record, WR
does have cool thematic angles to play with - humans aggro and tokens blend well with burn and +1/+1 counters and
Volt Charge, for example - but it's not a special "thing" all its own, which is something I'd like to see).
I've added more cards. I decided to proxy up the enemy fetch lands to get a better feel for how the cube will look with them. Another idea I was toying with was dropping to 1 each of the enemy fetches and going up to 3 each of the shock duals. I'm closing in on the 360 mark and want to get your suggestions for more ways to help out flashback and threshold themes. I also want to drop
Worldknit in and take another look at maybe running a second
Perilous Myr and/or
Epochrasite.
Worldknit scares me, but I pretty much never have more than 3 drafters, so maybe it's not too oppressive with a larger group (does allow obscene 5c goodstuff decks with practically no work, though). I think triple shocks is probably a mistake, too; I'm currently double fetch, double shock, single temple, and it's been great. Triple shocks sounds like a sea of 4c goodstuff to me which is not my taste and tends to make colour pair themes
dissolve, but to each their own!
