Note that we originally allocates irqs this way, and Keith changed it a while ago for good reasons. So I'd really like to see good reasons for moving away from this, and some heuristics to figure out which way to use. E.g. if the device supports more irqs than I/O queues your scheme might always be fine.
I still don't understand what this buys us in practice. Seems redundant to allocate another vector without any (even marginal) difference.
