I believe adding a guest option to the platoon NPC to add players with less rights would be a good feature.
I have no programming knowledge but I think it would be possible to add a dialogue to the base-gate that will ask the player which platoon base he would like to visit.
What I'd like in particular would be if I could get my faction's people into the platoon base to gear them up - and to meet up in general, without them having the ability to loot everything or having to leave their own platoon to do so.