Heya, I never commented on anything of yours, but have read ALL of it.
There is a smash like game coming out (hopefully) this year which was crowdfunded on FIG with a massive roster of indie characters: Bounty Battle
There's also one from Nicalis, but the name eludes me.
@Chomper Sharptooth: Spirits is a combination of the stickers(implemented in Brawl), trophies, and the event mode. Previously stickers were separate from trophies but that doesn't seem to be the case in Ultimate.
Not just hero of the storm but there are so many crossover games on pc it is insane. Mugen, By of a number of mods for warcraft 3 angel arena blackstar just to name a few.
When they first announced the Amiibo, I thought that was the plan, that you could use the Amiibo character in compatible games. What a let down when I learned it gave access to a sample of a game and a bit of goods.
I remember seeing one indie game crossover on Steam, but I don't remember the name. It is probably listed in
https://en.wikipedia.org/wiki/List_of_crossovers_in_video_games
Also, Google login is broken when posting comments.