I would imagine that any ship with turrets would have the same battery drain when firing weapons as any other player controlled ship. Maybe there is a battery separate from that used to power the jump drive and turbo, but it would still have a total capacity and recharge rate. The turrets could become just another weapon in the list, tweaked for fire rate, speed, range, damage and energy consumption. So that opens possibilities for tweaking it's defensive power.

Controlling the turrets is another problem, but I can see a couple of ways. Perhaps you can nominate targets which are automatically fired upon when they come into range by targeting them like we currently do, then pressing a button. Or perhaps you can set the turrets to attack anything hostile when within a certain range. Maybe selecting a target and pressing fire simply shoots from whatever turret has the target in range. Maybe all of the above are options. Lots of possibilities...

Player controlled turrets, IMHO, would be fun for a few seconds, but do you really want to sit in a Moth without any real control over the flight, while someone else drives you around the game on long and mostly boring trade missions? Me niether.

This experience of flying a moth heavy may be similar to flying a cap ship. Great expectations of cap ship fun may be dissapointing.