I want to create one, but there are 2 things I'm Trying to decide.
1. Should it be between Starters or Legendaries?
2. How much HP should each pokemon start with?
I'd use starters, there's probably too many legendaries for a game that doesn't drag on forever, especially if you include all of the ones that some people don't consider proper degenerates but still 'pseudo legendaries' (Latios and Latias, the bird true etc). I think there's something around forty - fifty in total.
So starters would be better, and if people enjoy it maybe try legendary afterwards?
As for the health, 15/20 would be a good starting point imo