The 16 in ML-16 I believe stands for the fact that the sixteenth prototype of the weapon was the one that worked the best, and so was the one that was ultimately sent out to the GTA. I'm not sure if this is canon or not, as I'm basing it off a half remembered, possibly fan written thing about there being 6 previous lab only versions of the Subach.
Wit reagrds to weapons, I don't think lasers would be all that uncommon. The TV War started in 2321, and while they obviously wouldn't have FS2 levelsof tech, that's still over three hundred years into the future, and with the rate of the advancement of weapons technology, I'd not be afraid to use lasers, even in the TV war.
Also, on the variety of ships, I definitely think this should be severely curtailed. Humans had been in subspace for a very short time when the TV war began, and prior to subspace it still would have taken several years for a ship to get even as far as Mars(assuming they haven't found some new means of propulsion that is, even so, it still would have been several months at the very least). Space travel just wasn't practical, and so there wouldn't be a lot of non government ships around. Just keep it simple, for the sake of logic if nothing else.