I wrote about these before, but I have more. So, here we go.
Color-Pie Break Cube
I’m not talking about cards that break the color-pie, but instead, I’m thinking about switching the roles of each color to something we don’t usually expect. This could be pretty hard, because some colors have a lot of different possibilities, but why not think about what green would look like as the control color? Blue can be aggressive (see faeries, merfolk, rogues, various tempo decks), but that’s not usually the role it has in cubes, so why not go for that? The rest can be a tad more difficult, but you’re smart and you’ll figure it out. Just shifting one should be enough though, as long as you try to take it into account when making decisions on the other colors.
Combat Phase Cube
No interaction, only combat tricks. I have tried to figure this out before and couldn’t do it, but maybe you can. Each color does have a different flavor of combat tricks and there have been plenty more flexible ones recently, so maybe this could work. Just a bunch of cheap creatures and cheap tricks. There are ways to make this more interesting like with Magecraft, Prowess, Valiant and Heroic. Maybe creatures that can pump themselves with mana as well, but that’s generally limited to very few colors. I guess, in the end, this is more of an intereting thought-experiment than a real idea.
Battlecruiser Cube
The complete opposite of the previous and this is what EDH was supposed to be before the constant powercreep. Big creatures, good decent interaction and the capability for many decks to switch between roles (search for “Who’s the Beatdown” if you don’t know what I’m talking about) quickly.
Weenie Cube
Maybe go the other way around and only have cards with costs up to 3? This can be difficult to pull of as you need ways to win, such as evasion.
French Vanilla Cube
Vanilla is a creature that has no abilities. French vanilla is a creature that only has keyword abilities. Keep things simple by not having complicated creatures. If you do this, you should balance it out by limiting the power of other types of cards as well.
Virtual Vanilla Cube
Virtual vanilla is a creature that becomes vanilla after entering the battlefield, so has an ETB. The problem here might be that the games might stall as creaturs are more powerful than spells and there isn’t evasion, but might be worth a try.
Purist Cube
Sick of all the cards from random Commander sets or pushed directly into Modern to force a rotation to a non-rotating format? Why not make a cube, where only cards that were in Standard or Type 2 (the original name of Standard) at some point. For pricing reasons you might want to leave out the original duals (they were kind of forcibly shoved into Type 2 back in the day). You may or may not leave out cards that were banned at some point.
Alternate Rules Cube
Every now and then Magic Arena has something like Omniscience or Cascade formats, where everyone has Omniscience or the first spell of each turn has Cascade for each player. Maybe not something quite that powerful (and there are good Omniscience cubes out there), but maybe something like you get a treasure at the beginning of your turn if you don’t have one (encouraging you to use them), or all activated abilities cost 1 less (with mimium of 1). These would open up weird new avenues for the design of a cube.
One Card Type Only Cube
Creatures would be the easiest, but maybe there is an opportunity to make a cube with Sorceries only? I don’t know. I didn’t really research this, but enough sorceries make tokens that it might be possible.
No Creatures Cube
Or maybe just cut out all creatures. This might mean that you have to take some colors out completely, but it’s an idea…