The whole concept of not being able to use your own weapons kills the Armas idea, why buy weapons when you can't even use them in Riot Mode, (yes, you can buy your loadout, but that is if you get enough money and survive enough to do so.)
So, players who have been playing for years, spending money on weapons see their money waster in RIOT, and newbies will just not buy anything because RIOT makes you pick up random weapons.