Have an option to reorder the request queue such that each requester's first song appears at the top of the list, then the next song from each requester, etc. The goal is to get new users' requests played sooner, and avoid a single user from monopolizing the queue, regardless of how many requests each user is allowed to make.
Subs & VIPs could get additional weights, so their requests are included with more frequency.
Example, Users A, B & C make requests in order: A1, B2, B3,, A4, A5, C6
The list would be ordered: A1, B2, C6, B3, A4, A5