I gotta point out at how I'm impressed many modern metroidvanias don't implement magic or similar techniques based on careful inputs in their games, as seen on SOTN's spells.
I didn't figure out all the combos but when I saw the spell where Alucard teleports and throws fireballs (like his dad), my response was "Oh, cool, a spell I'll never use". It wasn't practical enough to warrant the inputs and I wonder if that has anything to do with its disappearance from metroidvanias.
I'd like to see the god-gameplay and avatar creatures from
Black & White combined with the gardening simulation of
Viva Piñata and the TBS of
Final Fantasy Tactics. I was never a fan of large-scale simulation games because they felt so impersonal to me. I like having greater interaction with the individuals that make up my game world.
Ideally, my mashup would be a more grounded god sim that encourages investment in characters' skills to create an Eden-esque garden for them to thrive in and to make their mark on the world through travel, trade, negotiation, and combat.