Just a general question; what are some archetypes or gameplay pillars you would like to see in a cube environment, that there currently doesn't exist support for, whether that is because of power-level reasons, color diversity, card density, or just because it outright doesn't exist? I'm looking for inspiration for custom card designs, so feel free to go as wild as possible, given it's something that you earnestly perceive as desirable, and not just to be wacky.
As an example, a gameplay mechanic I've toyed with for a long time is the concept of graveyard cultivation, where you are encouraged to manage the content of your graveyard in a way where the presence and absence of cards in your graveyard are equally important, so that you can't just simply play a lot of self-mill to turn it on. An example from old-school magic would be Death Spark, while a more modern iteration that doesn't rely on graveyard-order could be Surreal Memoir.
As an example, a gameplay mechanic I've toyed with for a long time is the concept of graveyard cultivation, where you are encouraged to manage the content of your graveyard in a way where the presence and absence of cards in your graveyard are equally important, so that you can't just simply play a lot of self-mill to turn it on. An example from old-school magic would be Death Spark, while a more modern iteration that doesn't rely on graveyard-order could be Surreal Memoir.