Thank you Ravnic! Yeah I think you found most of my current concerns with the cube ahah
Regarding fixing: I think it is partially desired, because I do not want people to play 4-5 colour nonsense with all strong cards and without synergy. That's why I followed the original MMA design and put only basic landcyclers as fixing: we have three full cycles (
Gleam of Resistance,
Eagles of the North and
Landscaper Colos) plus a couple of "five colour" fixing lands, and the Vivids. I think this should be enough for two-coloured and maybe also three-coloured decks, but I am open to advice!
The arcane stuff... I don't know. I usually alternate between "the arcane deck is unplayable" and "the arcane deck is the most powerful thing I have played in my life". The problem is... I don't know which one it is! Since I have not yet played irl with the Cube, all of my testing has been just in the draft portion and not in the gameplay. Sometimes I think that
How to Keep an Izzet Mage Busy is busted because it basically is a permanent that can't be interacted with, and permits perpetual milling, damage prevention, and remouval... some other times maybe the deck falls apart by itself. I hope next summer I will have time and friends to draft this Cube and see how the arcane deck works!
Yes, the drafting on rails is also one of my biggest concerns. That's why I am very happy for the printing of cards like
Tribune of Rot, that I feel like is perfect for my Cube: it slots very well both in the BG Dredge archetype and in the GW Thallids archetype, but I would consider it also in a BR Goblins since the self mill and the tokens are very nice for cards like
Warren Pilferers and
Dark-Dweller Oracle, and it doesn't feel out of place even in any other black or green archetype.
One thing I was considering to prevent the draft to be too much on rails is to branch archetypes out of their original two-colour combination. For example, in MMA the Giants archetype is just Boros, but recently there have been many nice Izzet Giants (like
Aegar, the Freezing Flame and
Invasion of the Giants) so I could consider making the Giant archetype for example centered in Red, with the possibility of doing either RW or UR or even Jeskai Giants. A similar thing I already did for the Arcanes archetype, that branched into white for
Candles' Glow and
Ethereal Haze (so, Arcanes is either UR or WU or Jeskai, or even UB if we lean heavily into the mill plan, with cards like
Stream of Thought and
Mind Funeral). I could add black Saproling-makers, or red artifact-matters cards, or blue Storm payoff, etc etc. But then there is the risk that everything becomes a soup of colours, and I wouldn't like that too much...