Gain prominence with successful operation against the enemy --> more recruits --> establish more hideouts to house them
Hideouts would be a sort of pop-limit (but a soft one). The occupiers would have to find these hideouts from among the civilian houses. It would be a sort of whack-a-mole in that sense, but they can't just raid at random any house they want, as this will create more recruits for the GLA, but they'll have to capture enemy operatives, interrogate and based on that intel, raid the buildings being used by the GLA. Hideouts would be not be as important as weapon stashes however.
Weapon stashes, the production buildings, would be much harder to replace for the GLA. Thus concealing them well and hiding the traffic in and out from these stashes would be important for the GLA player.
Perhaps the GLA would could also use mosques for their operations. Holy sites would be inaccessible to the enemy, but could only be used as temporary sanctuaries.
Also, perhaps the GLA could farm narcotics in the countryside and smuggle them across the border (outside the map through border crossing points) for income. This would be their main source of income and they would use that to buy weapons (new weapon stashes and money for new units).
GLA economy would look like this:
popular support (provided by the success of your operations and the mistakes of your enemy)
hideouts (provide manpower)
farms (provide cash through narcotics)
weapon stashes (production)