Pretty simple suggestion, but it's definitely not that important.
I'm personally a big fan that Random Crits are now Melee only, but their random nature still presents a few issues I imagine. An option/server setting to make Melee hits function like the Gunslinger (Hit 1 > Hit 2 > Crit) from Live TF2 could feel a lot nicer/more consistent/strategic.
Melees that don't get Crits would still obey that rule, but just ignore the 3rd-hit-Crit mechanic I imagine.