Proxy etiquette: how to not be That Person Printing custom cards is the easy part
Here's where I'd start with building around Naban, Dean of Iteration in Standard
Instead, if Rally the Ancestors or Collected Company decks do end up being too good, I expect those namesake cards to get hit due to the risks created by cards like these in non-rotating formats where every new creature printed has the risk of making those cards broken all over again
Another iconic piece of Final Fantasy is the magic system
The new card Destiny Spinner is particularly nice since it only costs two mana, has a decent-sized body, protects your creature and enchantment spells from being countered, and is itself an enchantment
Ravnica: City of Guilds (2005) brought the most popular black card draw card ever (but only because the better ones are banned)