I haven't played the game it was in, but that Seaside Market stage looked fantastic.
If those fan favorite stages wont be in at launch, i hope they support the game post release with stages on top of costumes and characters!
I'm sure there's towns n all that mentioned in lore that could make decent stages. It's not like they'll take League and just put fighting game inputs in it or something lol. I'm actually excited for it because i love LoL, but hate playing it, at least when i'm not with a full group.
I'll get it on Ps4 because that's where most of the people i'm gonna play with are. Also, Share Play to make friends that arent into fighters play with me. Hopefully. Might not work this time since tag is out.
My current favorite is Dezmond Xavier. Hope Impact gives him a good push soon. The new LAX is great too, having Konnan as a manager does wonders for them.
All time fav is a bit hard to answer, but my childhood favorite was Vampiro.