I think it's very important to have them in a class of there own. My biggest complaint with running them together is safety.
Most that run brushless take way more chances trying to clear what nitro can't. I've seen several turn-marshalls almost get knocked out because with the sound of nitro, you can't hear the electric sneaking up on you. It can be tough and nobody likes to turn anyone away but it can turn into a safety issue really quick.