The main issue is that you can't change gear sets while in a cutscene. So if you're doing anything on any other class, you're forced to skip the scene, or take the penalty.
I'd say there are a few options the devs can choose to fix this.
1) Make the commence button change your gear set during the loading screen to the one you had active when queueing. (or if you weren't using a gear set for some reason, just equip any gear set with that class's weapon. Otherwise, just equip the weapon)
2) Let us join the duty no matter the class, but don't open the circle until everyone is the right active class. (and maybe flash a warning on screen that you need to be X class to proceed. do it within a minute, or you're kicked and get a penalty)
3, probably the simplest) Add an Un-start option to the cutscene skip dialogue box. That way, you can just back out to before the cutscene started, the same way as if you joined the duty, or closed the game client.