My thoughts so far.

I just played through the campaign from start to finish on Legend and absolutely loved it. You have made yet another fantastic game.

I really like how you tied in lots of the requests the community made in Harbinger (namely boarding). It's awesome that you take suggestions from the community so seriously.

The balance here is excellent, and it's truly an excellent game.

I've been thinking a lot about the constructive feedback I've read here, and it seems to fall into a few buckets:
1.) Research is less than ideal
2.) Marines need a tweak

First, research. I don't like using the word "fix", because doing so implies it is broken. However one interesting tweak might be allowing each sector you capture to let you unlock one specific research item. As long as you keep that sector, you keep that item. If you lose the sector, you lose that item.

To balance the whole "well what do you do with research units in-game" question - perhaps you could make those apply only to repair, or some other creative use?

Secondly, marines. I'm playing through a second time trying to focus more on boarding. I'll let you know if anything comes to mind as I didn't unlock the marine clone the first time around.