In regards of OC characters, like I said I feel like bringing some from my RP (Heroes Rise), which involves two characters as followed:

1). A Pirate Queen unit which acts a bit like Mccree in the style that she is a modern pirate and such.

2). A Robot Engineer unit which acts like a combination between Symmetra and Torbjorn (with a little bit of the TF2 Engie).

And 3). (A concept that never came around) An offensive unit being that of a sentient Raptor dinosaur, with armor and a gun. Acts like a faster version of Winston (King Kong vs Raptor eh?)

As for Canon, like I said, Soldier 76 will be the main one I'd like to use. May use Pharah or Reinhardt as well...