Agreed! And xp for resupplying vehicles with the ammo module, xp for when people get kills or assists while manning your turrets (similar to how drivers get some xp for their gunner's kills and assists), and maybe even xp when people spawn vehicles from your terminals or use cortium from your silo.
Building a base is so wast of time in witch you could earn certs. Building is not exp rewording. You could also add time exp reward for HIVE owner.
Some of us don't need certs. That said, being in proximity of the hive does give a bonus. I do like the idea of added directives to construction. # of infantry spawns, # of vehicle spawns, Minutes of Active hive, or a tally of %ages of hives maybe? Squad/Random construction pulls from your silo (IE, each time someone pulls and places a modules from your silo, etc) There is definitely a bunch of possible directives that could be added if they have the metrics being tracked and would help with the cert gain as you gain both ribbons as well as directive rewards.