I thought they were already capturable. You're supposed to capture the port the TG is assigned to after you sink the CV. Once the CV respawns its your team's. This might have been changed though to prevent uneven odds.
He wants the Base Capture points for sinking it after you have already captured the port.
If you bomb a CV and sink it, why not be able to get the base capture?
i think you just want the perks, cough cough, scorehoar