Yeah, sometimes FIA get crushed right at the beginning. when that happened my first step was going to the towers to flip a radio and see whos online. That was removed in 1.8. Text chat works but most don't read it (console players, limited response). Sometimes its just hard to stay together, even with a tent, as supplies and tent location are always an issue. Gets worse is the cache locations arent favourable, or have been raided for supplies. Your concern with endless running is 100% an issue. I often get stuck trying to find a car or open supplies and often die at that stage as its facing the major teams head on for them before getting a rifle. random spawn > find cache > find car and supplies > back to cache > get tent and rifle > drive to operating location > deploy tent. Even if you manage to complete that loop, and you die, your still limited to 5 respawns on that tent and hopefully you can recover (or aquire) new gear.

I'd suggest being able to buy tents at enemy arsenal, but then i would just put it beside their supplies and mooch every spawn with very little effort. We can already access enemy arsenal to buy weapons which is core, I think being able to aquire a civilian car at a enemy depo would eleviate most of the walking.

Being stuck at volunteer limits access to mines and c4, which is the best way to limit movement and base access for the major teams. If you somehow get a construction truck, back to the supplies limit, generally less effective and a larger target. Mines are the best tool for FIA.

Maybe minor points, but as a guerilla warfare enjoyer it might be too much back/forth if points can be completely taken. Slow retake process would really destroy a team. Thats why I keep coming back to something with Radios/Comms.
Actually, bigger thought. Vehicle based, or deployable radio jammers as a unique fia item. It would block out points and radios in a specific map radius. Consume supplies on a timer, like a draining battery. Show the deadzone on the map for everyone, and have the jammer be somewhere in the middle. Have deadzone block all radio and comms, even bases. Would make the major teams have to respond quickly, but in a way that doesn't take a ton of time, and maybe give the teams another reason to work with the FIA. Would give FIA encouragement to work together as it would extend the amount of time a team could respond to an issue.

The punishment is good for FIA, I think. 1.8 made it too much with the death cycles FIA goes through though. Sometimes its unrecoverable. Go from captian to volunteer just trying to get a rifle with no real way to level back up (only small squad work in most cases).