I would like to see the magazine concept approached in a different way. The FP-90 mags are possible by top loading, and ammo carried sideways as in the 5n7 rounds they use. A bull pup design with the ammo mag on top acting as a cheek weld versus the mag in the bottom might also be looked at.
Bull pups have their place IMHO. They deserve a better arraingment/design but the concept is valid I believe.
Stay Safe !
Getting abraded with sand etc won't be a problem if they come in sealed battle packs, and you toss them after one firing.
(Of course the enviro weenies won't like that battlefield littered with 'non returnable' mags, among the corpses.)