When a team Is advancing, and building new advanced FOB's and HAB's, fairly often the old ones gets either left abandoned or players got to return to the radio and dig it down.
What I am suggesting is that the Commander of a team, can when moving away from a radio start a counter on it, that lasts for 20 minutes.
You could make it an "upgrade" that the radio has, which would cost it like 1000 ammo and 1000 build, to make it into something you have to account for.
Put down a regular radio, supply it with ammo, place a specific TECH unit on top of it, dig it up, and it could change the model to one with a lot of explosives on it, with a visual clock?
If the counter is not stopped the radio despawns as if it was dug down by the team, incurring no loss of tickets.
If an enemy finds the radio and digs on it, the counter is stopped and they can incur the radio destruction cost. Alternatively, if the enemy finds it and does not stop the clock by digging, but opts to place an explosive like C4 on it, the explosion should take out the whole radio as the counter would, and incur the cost, without the bleedout stage. This would make engineers/sappers/etc more valuable.
It might give a slightly different sound that the regular chatter nosie, to indicate to people nearby that its "abandoned" or not, depending on how you wish to implement this if you do.
This will enable the players to trigger a FOB to despawn, and no longer need to manually dig it down when advancing.