That's how I feel right now. Hacking can get pretty annoying with all the little glitches and errors that come out nowhere, making even the simplest things such a pain. Maybe I'm just tired and later on I'll change my mind. But if I ever hack again, I'll never hack Emerald. It's an awful ROM for hacking, IMO.
I likes your avatar, I always watch him tip his hat when I see it!
Not by any amount that would be useful, unless you want to rewrite half of the game engine lol.
The Gen 1 and 2 games only use 1 byte to store Pokémon IDs, which would give a max of 256 slots. However, slot 00 and FF can't be used, since those are used to mark the ends of certain lists that contain Pokémon IDs, bringing it down to 254 total IDs. In addition to that, the Egg takes up an ID slot as well, making it a total of 253 usable IDs. And since there are already 251 Pokémon, that means even if you go to the trouble of repointing data to make room for the new entries, you can only add 2 more Pokémon without replacing anything.
If you want more than that, you will have to:
1) Learn ASM
2) Track down every routine in the game that deals with Pokémon IDs
3) Rewrite it to handle 2 bytes for the ID instead of 1 (probably not as simple as it might sound even once you found them)
4) Update all the data containing Pokemon IDs to use 2 bytes instead of one, such as Trainer teams, wild Pokemon, givepokemon scripts, etc.
Basically, the long and the short of it is if you want more than 251 Pokémon, you're way better off using Gen 3 than Gen 1 or 2 right now.