You can allways have 2 rockets in rpg style weapons no matter the carrier.
With heavy you have them ready, no kit or the small one you just tap resupply to get a spare one.
I think this would be a better system:
No carrier= Only the preloaded rocket
Light carrier= Preloaded+1 spare.
Heavy carrier= Preloaded+2 spare.
The third rocket can be justified the fact that maps are so big
that there are insane amount of camp spots that need to be cleared.