Unfortunately i don't know someone who can really help you. :(
Changing sprites to HGSS is really a good idea: it will give the game a more professional look. I think you may want to discard the idea of fakemons unless you are (or you find) a really good spriter. Custom tilesets and pokemons are good only if they are well made, because thay have to fit with the Nintendo's ones, which is not an easy task, really! I'm sorry i can't be of better help, but i'm not good at anything because i haven't tried anything. Maybe i could be a mapper, but i'm not sure... :knockedou
P.S.:The banner of your game looks good an the title screen is good too!