Siege bloodlust

[Sniper]

Maybe we should implement a rule that gives the chance for the owner to pay quarterly "tax" or something like that, before the enemy start the siege. Don't kill the goose that lays the golden egg. Just an idea...

Yep! And over time things change. Occupying forces get pushed back, PoB's are still there, Win-Win. RL has given us the blueprint.

Counterpoint:

Money is not always the goal; it does not make sense for an enemy military to be accepting money or goods when the base still exists and can be used as a vector for infiltration or espionage. Furthermore, a lot of factions don't want to inherit a POB via capture because it's a burden on their players' time.

Depending on the demands of the annexing force who probably would require access to the previous forces to be curtailed. Even, as Champ notes, get the base to change its IFF, if that is possible. The RP opens up to endless opportunities.