Still the best of the original starters by so far in competitive terms (Last I saw anyway, gen 6 bullshit probably changed it)
I swear i originally had dragons and dinosaurs and shit with canons etc written down. anyways it doesn't change the fact that gen i was cooler so suck it.
Definitely use Gen 6 mechanics if you can. In terms of Pokemon, just a mix of whatever you like IMO. It's your thing, so it's your region/universe. If that means mostly Gen 1 but with a Froakie in there then so be it.
I've got nothing against Charizard ftr. Charmander is still probably my favourite starter. Squirtle and Bulbasaur can blow my Greninja and Serperior though.
Trying to fit some sort of mechanic for like EXP share or other classic items I don't mind but megas and shit definitely could get way complicated. Up for debate really.
If you just include favourites though it's going to screw with the game balance an- [remembers pokemon has not made any attempt to be balanced]