the starters part just sucks - just doesn't make any sense to have the legendaries be owned by a trainer
it'd be more realistic for the time period if they didn't have real starters and you had to begin with a pidgey or a boring early-on poke
at the end of the game you could maybe get the opportunity to catch all of the final evos of the first gen starters in some endgame event
the rest of the idea would be cool tho - even tho i assume catching the pokemon would end up being a lame gimmick like in pokemon ranger or mystery dungeon since pokeballs weren't invented yet