I know this is weird but I think it would be cool to have the starters be pokemon you would normally find in-game, I had something odd in mind for starters like Staryu, Cottonee/Petlil (Depending on the game), and maybe a growlithe as the starters, just for variety, and also maybe make like a section that was like a "PokeTransfer leak forest" as some people in bw1 refer to some pokemon having been leaked; maybe to put celebi and shaymin there. Also I like the idea (and ik this is extremely hard) but maybe you could make the types of pokemon change by day (i.e. pidgey and rattata on monday, hoothoot and pichu on tuesday, caterpie and weedle on wednesday, and so forth. It makes it a lot easier to find and catch the many pokemon in the game. All pokemon should evolve by level, and if the poke does evolve by stone or trade it should be at level 30/5 levels after the pokemon first evolves