I think that if we use riot shields for anything than it should be in a way that has adjustable rules on the fly per game and narrow down the fairness.
1) As a starter, maybe all riot shields are a small size, covers torso area. If someone opts to use it than they either use a single handed weapon like a pistol or Mac10 (Mp5 i dont think counts)
2) (a) A person has no weapons but a shield and follows a teammate to provide mobile cover. If the teammate who is providing cover goes down, the other member may not pick up the shield.
(b) The if the shield person does a bad job and his teammate is shot or wounded, the shield person may switch to protect another teammate, or lose their shield (for the game) and use a weapon.
3)anything else to add?