[Raellus]

Wouldn't those vehicles "left behind" by departing REFORGER units be packed up and shipped after them, as replacements for combat losses? I would imagine that this would begin ASAP.

There's no way new production alone would be able to keep up with losses. A lot has changed since the "Arsenal of Democracy". An M1 is a whole lot harder to build than an M4 (i.e. costlier and slower production). Perhaps this justifies the introduction of the easier/cheaper-to-build Stingray and LAV-75* early in the war.

*I know that this design really never left the drawing board and has been poo-pooed by the T2K community. But it is plausible that such a platform could have been designed and put into production fairly quickly, especially since it is based on an already established AFV chasis.