There's lots of different mentalities when it comes to building around commanders. Unfortunately the kind that is the most accessable: get a bomb of a commander, like 2x etb, is also the most vulnerable. And I absolutely hate Tron style stuff. Or at least I don't want to deal with many of them. I wouldn't mind having some that deal in more or more interaction. I already have my legendary deck that deals in making people combat. I could probably upgrade a few of my decks to make the power levels closer to what people here at BYUI play. But I think the deck I'm most fond of is my Atraxa proliferator. And I think I could probably change out the commander to make it less 1st turn targeted and it would still function just as well. So, what're the other mechanics I'm interested in? Well, I did make a list at one point.
Anti artifact would be really interesting. So would stuff that significantly changes gameplay, like by suspending cards. Would grouphug but through giving everyone token creatures be fun? It might clog up the board though.
Oh man, I would not mind a choas deck at all. I could play with it to decide how much chaos for the whole table or the power level, but I love the idea. Playing with other people's decks and mill are also real fun ideas, in my humble opinion. And mill would give me a compelling reason to lock people out of their graveyards. Also running crazy tribes would be really fun. Werewolves could be cool.
Life is a resource is a fun one to fiddle with, kinda my own way of playing with danger. And it's black, which is like the best. Alternative wincons could be fun, but I'm leaning more towards more interaction rather than less.
Also, 5 color stuff like Jorah is way cool. I like the idea of cheating out massive spells.
What about shrines and gates?