That's how I've been handling things. I give HE a burst radius of course ( as per grenade, but varies by caliber ).
Baton ( rubber ) rounds are pretty dangerous if they are used at close range or hit the head. Maybe the target gets an "easy" save, failure resulting in L-type?
Your suggestion for flechette is in line with my model for soft-point/hollow point/dum-dum rounds.
I also give tracer rounds ( from machine-guns typically ) an extra 1 point of fire damage, persisting for 2 rounds. I roll a d6 for each burst, on a 1 a tracer round is the damaging hit.
Also there are the "smoke" munitions ( grenades, mortar bombs etc. ). Some merely present an asphyxiation hazard in enclosed spaces ( vehicles and smaller buildings/rooms), but many military versions are actually white phosphorous weapons, essentially a flame weapon whose damage potential persists, undiminished, until starved of oxygen or fuel. ( it will re-ignite if oxygen supply is restored ). I apply full damage for 5 rounds, then reduce a point per round. I apply random initial damage.
I'm sure there are other tweaks I've made that I can't think of now....