Yup, Wolf Starslayer is correct on all accounts. You can also restrict what gunners are able to use via the Ship panel - or, if you want to go the extra mile, just power those down. Unless you plan on using them yourself, of course.
Also, I've had MC seats open both before and after DW2. Since the expedition started, I've had three players just come in, not say a word, then leave after a short amount of time. (Not a crash or disconnect, mind.) That didn't happen with any of a dozen players before. Might have been because they checked my Cutter and decided that it wouldn't be worth the effort to fly to to gank. So yeah, take care if you decide to host.