As an avid airsofter, I was reading a lot of this, knowing only vaguely of what paintball uniforms consist of. What it looks like the biggest concerns are mobility and heat exhaustion. Both of which can be fixed by trial and error. Instead of doing all of that and taking it to the field, what I did for all of my airsoft gear, was going out for a jog around the block with a friend of mine. He was making sure I was doing okay and keeping me safe from cars etc. If I found something was getting too uncomfortable for whatever reason, we would stop for a bit and talk it over, then come home and talk about ways to relieve this problem.
As far as your idea of making a "shell" to go over the paintball helmet - I think that's probably the better way to go. I took an older helmet of mine (one that had crummy padding) and revamped it to make a Samus Aran Helmet. I'm looking into making Samus armor in a similar way to making the Halo armor, but that's still in the works. Essentially for the Samus helm, I have the paintball helm UNDER a layer of paper maché. I just made sure to keep holes in it for ventilation and I put a motorcycle visor under the paper maché and over the paintball one. I don't have any pictures as of this moment for the internal of the helm, but the external looks quite good, in my opinion.
My point in all of this was to say that I know that I've done something that while not tested, it doesn't seem impossible. Since you're dedicated to making this happen, I don't see why you're getting so much hate. You're just asking if it's possible, not whether or not it's practical or going to be the best armor on the field - you just want something that meets minimum requirements and looks cool.
Best of luck to you.
EDIT: Just as a note, my airsoft gear is just several layers including TRUs, a vest, and a helm - I was used to just wearing street clothes. It's not anything fancy, really.