This is mainly just for my Fanfiction piece that I'm writing, but an idea I had for an ability is Imitate. This only works if you're around other people who have supernatural abilities, but my idea is that you can imitate an ability, if you use Imitate while someone is using their abiltiy. For example, if you used Imitate when Emily was to use Domino, for example, you would be able to use Domino as well. However, you can only Imitate up to three things at once, one normal Supernatural Ability, one passive Supernatural Ability, and one Bonecharm that is active. This wouldn't be practical in-game, however, I think it's pretty cool for a fanfiction piece.
And the upgrades would be more Abilities that you can store, or something like that. If you have any suggestions, let me know. Also, here is a link to my Fanfiction piece.