Hey look who's shooting for Centurion. Great build Greg
As for your list:
1 - paint the latex hand guards and glue them on rubber chemical gloves (for Centurion), YES
2 - fix sniper plate/thigh overlap, I think you're ok
3 - replace large ab button plate (aesthetics), If they're molded, not buttons, I think you're ok
4 - tighten up the ab/kidney plate join (for Centurion), Eh! yea it could us a bit of tightening
Only thing I would add, though it shouldn't effect EIB (but may effect Cent) is the left TD belt clip. I would suggest moving out to the edge, flush with of cap.
Also, for Cent your Hovi Mic tips will need to be white in the center.
Looks awesome