To be honest, the JLS FN2000 will not work for you. It is very cheap for an Airsoft gun, and a decent one at that. Use a JG AUG. As a base it's excellent, JGs are reliable, it's bullpup, and it's very futuristic.
Or a FAMAS. Both will work excellently. I would buy Adam's cast and try to fit a disassembled AUG into it. But please don't do it if you don't have experience modding Airsoft guns.