This cube is about The Rack, a card originally printed in Antiquities. You will try to rack your opponent out but not get racked. Mostly though, it's a cube about family.

Remember, it's all about the rack. Fun is not one of the design goals.

It's important to analyze the relationship between primary, secondary, and tertiary cards and how they'll work in this cube.

It's important to keep in mind the relationship between lifegain and life loss. Life gain is inherently worse than lifeloss for your opponent, because you're not getting any close to winning the game, unless you add some sort of rule about winning the game at a certain life total. Therefore, lifegain needs to have immediate payoffs to be worth it. Another aspect is that lifegain slows the game down, while lifeloss doesn't.

Try to ensure there's both enough interaction, but secondly that the interaction isn't too crushing. If someone builds their deck around an entire strategy and the removal is too efficient for it, that might be an issue.

Might want to have different clear avenues to win. One through damage, so multiple damage sources stack. One through milling. One through poison maybe? One through lifegain?

My intuition tells me that in order to have "aggro" decks and "control" decks, the colors that are good at making the game go long should also have tools to win once they have amassed enough resources.

Each color should have a pretty clear way to win the game, and there should be interesting overlap between most color combos.
White: Lifegain? Second Sunrise?
Blue: Mill
Black: The Rack
Red: Burn
Green: ???

counters and proliferate?

There's so many different non-creature archetypes, but they don't intrinsically allow you to win the game without creatures. Creatures are amazing because they have unique effects on the game, and they have a clear way to win the game (doing damage). The rack cube doesn't have that.

What good is Eggs if you don't have an obvious way to win once you have all the mana and cards? You could presumably find yourself in a situation where you literally can't win the game by any conceivable way, and if you only have like 3 racks in your deck, you can just use 3 artifact removal spells and win.

Possible ideas: everyone has a The Rack emblem that will deal damage to them if they have 2 or less cards. They could also choose a black vise emblem.
-wincons are indestructible but enablers are not. So the rack is indestructible, but the Bottomless Pit isn't.
-custom stuff on cards to say you win if you do X thing.
-a different part of the draft where you draft all of the wincon cards.
-a backup way to win the game that everyone has access to (after the game you get 3 copies of the rack, black vise, millstone, darksteel reactor, maze's end, mirrodin besieged, revel in riches, test of endurance)