I love playing with stats and equations. Do you have any basis for how you are leveling characters in comparison with monsters? If so it's mostly a matter of plugging and chugging and a bit of re-balancing from there, which sounds fun to me. If not, then I might can come up with a few mockups as far as possible stats for you if you'll tell me roughly what you're looking for.
For instance, if you have 100 HP, 20 MP, and 10 for all stats for a level 1 character. Enemies should be roughly around those stats (a bit more or less depending on party size, monster party size and skills available).