Ok, just got back from helping a mate with something (needed sparkplugs changed and didnt want to pay a shop to do it lol) anyways let me answer a couple of questions and get to repairing the IPS.
As for Eevee, you are correct. The way it went in my head was "Ya know, Eevee was SUPPOSED to be your starter in Yellow, but Gary snatched it. This time Gary wasn't paying attention so HE gets stuck with Pikachu. Lets see what its like with Eevee for a starter!" and that's how it came about. All Kanto starters will be obtainable as well. Eevee being your starter, Pikachu being catchable in Viridian Forest, and Charmander Squirtle and Bulbasaur will be obtainable in various places like they were in Yellow, albeit in different ways and different places.
If you all want me to keep te Raticate guy in as a challenge, I can always change him back so he will stay that way when I remake the IPS. I'll let you all vote on that while I fix some other things and whatnot.
The 500p Magikarp guy won't be in the demo, I'm still learning how to make you buy things with scripts, but he will be in the next beta. Right now someone just talks about it. (well he will once I retype that pointer and HIT SAVE THIS TIME *embarassed*)