Well in case you somehow missed it, there are two hacks; one being a complete demake and the other taking Sinnoh and throwing changes into it
I'm not a fan of the old EXP system either, but I'm reeeeally not a fan of the new one. IMO, a custom one should be created, but I'm not doing that soon
Oh,that sounds good also.Hopefully that will make the game diiferent exprience than the original.
Also you can plan to add trainer ev system,which will make it more challenging too....(the original one was little bit easy...except Garchomp)
Also will you update the pokemon abilities,or add new more ability from GEN 5,6 ?