It makes sense to introduce priority queue for specific types of transactions. F.e. in time of high traffic it would be preferable for witnesses to be able to include transactions that change blockchain parameters (like increasing max block size), because they can fix congestion that way. Also some operations are time sensitive, like account recovery or canceling "decline voting rights". However I'm against allowing wealthy users to use their basically unlimited RC to outbid normal users from transacting on blockchain. If we ever do something like this, it would have to be fee that burns actual Hive, not RC.