Aw man I wish I could have started with Bulbasaur
dude just cheat one up, its a beta and there's no anti cheat or multiplayer and nothing past the 1st gym. once you've played that normally there's nothing stopping you from cheating in pokemon, you should be able to use all gen 1 and 2 pokemon, but there may be some bugs with the ones that haven't been tested (the ones outside of areas we are working on)
to grant yourself pokemon open party.dat and box.dat in your save folder, each line in there is a pokemon with their current stats, evs, moves and so on. you have to copy another pokemon and change some of the values to suit what you want. you can have 6 pokemon in party.dat, box.dat is for bills pc, you probably want to just add things into the box and get them out in the game than put them in your party.
also it should be possible to add pokemon that can look like whatever you want as long as the sprite is no bigger than 128x128

the system for pokemon species is now data driven
oh and if you actually mod the game files and not just your save i'd back up the game to somewhere else and edit that copy. if you're editing saves its wise to back your save up from before you messed with it. just copy the folder somewhere