Criticism: As DRG said, that Marnian house is being used a lot. With reference to the name, I don't see anything in the storyline that has to do with 'Illusion'. I was expecting something at least like Zoroark being controlled and making illusions so that people will leave a place and Team Jazz can take over it or something. And the indoors are quite plain. That's all ^~^
The fact that you have said you are including 4th and 5th gen Pokemon is a big plus, because I personally like hacks that have new Pokemon for me to discover. The Pre-battle mugshots are also a good idea but I'd advice you use it only on important battles like Rival/Team Jazz/ Elite 4 battles. Running shoes in buildings is also something that I greatly support.
Good luck on your hack! I'd definitely be playing when there is a release! And please take my criticisms into consideration. New hacks get those very often but that is what make that good hacks after the creators have learned!