Now that the 2800 series is over, I hope the devs can start rmeastering old missions again. I don't know anything about game developement or programming so this is only a guess at best but I think it would be easier to redo what's already there than to add missions entirely from scratch. You could throw in some cut scenes, a little VO when possible, add some new sets and VOILA! Sort of new content but comming a bit faster as most of its already done. I think it would also flesh out the game a bit better.
I bet you could convert a bunch into Klingon versions for their faction too like they have been with the FE. Can anybody on the dev team let me know about any upcomming remasters? Pretty please....with sugar on top?
I think remastering the episodes might be more important. Some of them flow pretty nice, but others are just a dreadful chore to do. You can add new content, but from what is proposed here... they'd basically be only ever adding new content, and the old stuff would just stay old and untweaked. Some of them could really use some tweaking, with how well the Klingon War missions open with their new Remastering.
Total clean up of anything wrong before adding anything new.
Anything with a balance issue, fix it.
Any bugs, fix them. Stuff like the decloaking dialogue bug is just lame. And the Borg seem to learn a new bug every other week in Ker'rat.
Then fill the gaps, namely, simple KDF missions as suggested above.
Last, tier 5 K't'inga, it's something that's been asked for, been told we'd get, and has precedent, and would allow another VA level ship in the KDF roster. Raptor basic stats//weapons with Excelsior boff layout/console slots would be a good starting point. Also, the K't'inga already being there means it won't need a 3D artist to dedicate time to it, all in all it'd be a pretty cost effective investment/return choice for Cryptic, and we'd get a bit more variety at the top of the KDF roster, which is noticeably smaller than the Starfleet one at that level.
Edit: Also, PVP obviously, some new modes would be nice, but word on the street is they've got a way of making new maps quickly in the pipeline.