To add on to Jagger's #7 specifically, 2-3 turrets will completely shred through a Munificent before there is any time for the GM to even properly deploy the frigate. If the operator of the turret is actually adhering to some level of "fire and then pause, then fire again" then the GM will have just about enough time to get the frigate into place.
I am all for players being able to dictate the direction of events- but a few small deployable turrets can completely destroy any chances of an assault on the base. This isn't really players shaping the course of the event. This is overpowered weapons getting the job done far too fast for most players to have a chance to enjoy anything (which is already something we see with flamethrowers and some other permweapons)
The Game Master's responsibility is granting items to players who need them for the course of the event. If the Game Master says no, then it's no. If he says yes, then congratulations, you get a turret. The time taken to do this is something that Game Masters & Helpers are trained to prepare for. It wasn't a problem for me when I was among the general ranks of the Game Master program, and I haven't heard anyone complaining recently that people are simply asking for turrets far too much.
I just wished to express a few more thoughts building upon my -1.