First off: I really like the new Raid mechanics, but I still want to hear about Conquest
On Crew experience:
Personally, I think you should have more differentiation so that there are interesting metas to pursue and not just one path to optimum. I miss leveling Crew, in the sense that it made you care about casualties; I entirely agree that just giving them one path was pretty dull (I still remember grinding Elites so that I could take on the Defense Fleet).
So...
1. Pilots, for attack craft.
2. Engineers, for CR repair and maybe ingame repair.
3. Gunners, for damage bonus (not range, not accuracy).
4. Flux Mechanics, for more drain / pool.
Rate them all, level them all. All Crew start off as Basic Crew; they specialize when they level up the first time, depending on what they got assigned to do (by the game, automatically). As they get higher in level, they cost more.
Sounds pretty complex, but wait:
1. It gives players a reason to respect Crew casualties again. This should, imo, be why players gradually transition away from Garbage Balls; sure, they're cheap, but they're just not as effective. If you don't treat your crew as expendable, and buy them ships that last, you get experience and "loyalty", in the sense that they're just better now. Throw in "trainer" skills for your Captains, and boom, you now have a Mount and Blade-like system where your Captains can offer nice passives to offset being less-stellar combatants (I really think this should be a thing; stuff like the Pathfinder skill from that game is missing atm).
2. It gives players a choice between cost and effect that's useful. All-Elites should make it possible for a smaller fleet to shine. It'd provide a counterweight for the AI needing ever-larger fleets, too.
3. It'd feel meaningfully connected to the Marines mechanically.
4. You could even throw in some Ground Commander skills for Captains, and complete that circle.
Anyhow, I like the proposed changes and I'm looking forward to seeing this next build quite a lot