Yes and Yes. It would be interesting in an AU and game play.
For Mechs and ASF:
A lack of parts/damage to the factory force the manufacture to downgrade from standard to primitive/retrotech.
An IndyMech/CF factory upgrades to produce Primitive BattleMechs/ASF.
An old factory is being refurbished but the best quality they can manage are primitive units.
For Vehicles.
Support Vehicles get upgraded to use more advanced materials making their vehicles as close to combat vehicles as possible. (Tech D+ engines and BAR-10 Armor.)
The factory upgrades to produce a primitive combat vehicle. The rules are in Mercenaries Supplemental II but the 20% tonnage for ancient equipment is kind of vague. You could house rule using primitive Mech rules. (Primitive engine, armor, and targeting.)