hum interesting, maybe we could include something like a profiler?
the best solution in my opnion is something like query_reponse_time plugin (function time histogram), it's a bomb to kill a bird, but usefull...
maybe include request count + total request time? or just request count? must check if this include many mutex or not, and if it create some contention (i think no, stored procedures normally aren't too fast to stop and cause problem with some single mutexes)

+1 for this request