The Spyderco Gayle Bradley and the Benchmade 760 are production M4 bladed knives.
Benchmade has done a plethora of M4 "limited" editions and Spyderco has the Military run coming up. I see little reason, beyond cost, for not having ar least one of these knives.
Not to mention the years of Benchmade M2 knives floating around.
Severtech autos are in A2. Mine seems to be well heat treated.
And there have been oodles of slippies made of carbon steels, such as from Case, Old Timer, Rigid, etc. And the old tool steel Gerbers.
You mention "properly heat treated". Not sure what that constitutes; max hardness, differentially, max toughness, or?