[Alastor Mobius Toth]

I don't think there's a track system can can reliably tow/move something as heavy as A-10.

Also, railgun technology wouldn't work, because it's too fragile and inefficient. IRL, the smallest railgun today is size of a destroyer, and is result of decades of work, millions of dollars, and can fire a shell every...several hours? M-L's railgun is smaller, but it uses G-elements (which are in short supply), and is incredibly fragile (LNs and Manga of TE show that it's utterly worthless if you get surprise-attacked). And yes, it can fire 2000 rounds in matter of seconds, but then it has to be reloaded. To BETA, loosing 3000 troops is an acceptable loss, especially if the next wave will overrun the railguns anyway.

Another thing is that Destroyer's shell is nowhere near as indestructible as most people assume it is. The side-materials suggest that it really is that though, but ML: Alternative VN (which is IMO, the source of all cannon), shows that it's inconsistent; Valkyries take down several Destroyers with frontal shots, and even sword blows.

One of the side materials implies that most forces still use Steel Penetrator rounds instead of Depleted Uranium/Tungesten sabots. While I'm not a military expert, steel-tipped rounds were obsolete towards the end of Cold War, and wouldn't do jack against modern-day tanks, much less armored aliens.

It would probably be more effective to simply increase the supply of quality ammo, rather than build new weapons altogether.

120mm cannons can also fire canister shots, which makes shotgun weapons redundant.

Really, for the most part, M-L's humanity would handle itself well, if not for the sheer attrition they suffered before decent technology became available, and the mind-blowing incompetence of several countries (Yes, I'm looking at you, USSR).