If a base has a static ammo container, have a button like full heal meant for resupplying AI, and statics/vics manned by them (Not vehicles used by players)
It might be a bit more problematic: the resupply action is baked into the squad_management.sqf (around L179-L200) so that should be extracted into a separate function for ease of use.
If a base has a static ammo container, have a button like full heal meant for resupplying AI, and statics/vics manned by them (Not vehicles used by players)