Damaged Jagermechs. Defective Blackjacks. Ancient Whitworths. Captured Urbies.
Only possible new mechs would be clearly garrison material, like Sentries and Watchmen.
Maybe the occasional working Centurion, Enforcer, or bug mech.
Worn-out Partisans, Strikers, and Goblins.
Excess Vedettes, Scorpions, and APCs.
Old ACs for field guns.
Boeing Jump Bombers, Guardians, and maybe the occasional Meteor.
Honestly, when you’re a state with hundreds of worlds and probably thousands of uninhabited continents, large islands, and outbacks, there’s no need to travel to and conduct training exercises on a foreign (if allied) planet.
If it’s really about training exercises, doing them on Small World should have almost no value to the AFFC, and Small World should get the absolute lightest and least useful dregs from the above.
If it’s about having an ally and a base in the Chaos March, then that’s more valuable and some of the heavier and better stuff from the above list should find its way to Small World.