Since we’ve already got a lot of heroes (yes, some of them need some buff or even a rework), I think it could be so interesting if we see some sinergy with some of them.
Instead of being skills, it could be an specific perk for some of them. Such as Wesson’s platinum skill, there could be some interesting heroes combinations. I imagine, now that we’ve got some sisters, a perk for playing with them (Siren + Maven + maybe one mech sibling). Perks for using a faction (such as damage bonus in bounty), etc.