I did a few drafts of this using the custom draft format with 4 sets, 4 packs of 8 spells followed by the land pack. I didn't feel like I was seeing enough cards to get my entire deck built. In the first two drafts, I ended up in Esper colors, and I found myself switching strategies in an attempt to respond the options available, and in the end I had a mix of about three strategies in the deck. Mind you, this could be due to bad draft choices and/or not being familiar with this cube. I ended up putting all of my playable cards in the deck, plus a couple more that weren't necessarily playable. I felt like I had some interesting tools to work with, but I didn't quite have enough cogs to make everything happen. I think seeing more cards would change things a lot. I don't know the ideal number of playable cards that you want a player to have for deck building, but it's more interesting if I have enough that I have to agonize a bit over which cards make the main deck, and it's fun if I can choose which minor sub-theme I run and which one not to run. For the esper decks, at least, it seems like more cards might even allow the type of match where you could board in a different sub-theme, depending on how game 1 goes. The discard, blink, artifact, and sacrifice themes all mix together in interesting ways, and I like those ones because it feels like I get to make something creative. The two Esper decks actually did look capable of pulling off some fun things.
The U/R spells draft that I did made that archetype seem well supported, but it was also a fairly linear draft. I ended up short of playables in spite of my efforts to look for a third color to complement the main archetype.
The Stax theme looms pretty large. I get pulled in that direction.
Anyway, feel free to be skeptical about anything I say, because I'm new at cube design.
By the way, your earlier post about "a really challenging post about cube architecture philosophy by Grillo in Inscho’s blog thread" caused me to go down a pretty long riptide rabbit hole. I found the post in question and also had a good time reading some of the other stuff along the way.