Very interesting, but I already maxed out my "looking forward to play this update" already... Oo
Fair

I have a couple of questions though:
Does construction rigs have any role regarding recovering ships during the battle? Or do they just stand back in a corner?
During battle, absolutely nothing. Post-battle, also nothing, but thinking through some possibilities (sort of as an on-demand Reinforced Bulkheads? but more to think through there).
And how does the variant auto outfit manages mods? If weapons have to mention what they are upgrade or downgrade of, it could represent several hundreds of weapons to check with all the currently active mods. What kind of tags can we expect to have?
It creates some halfway-sensible default tags if a weapon doesn't have any. Tags are stuff like "pd<number>" or "kinetic<number>" or "strike<number>". Higher <number> means "better at the role". There's also a "SR" tag that means something is short-range; what this does is make sure a long-range weapon doesn't get replaced with a short-range on unless it's PD.
Some weapons have multiple role tags, e.g. the Heavy MG has: "kinetic11, pd10, SR". Meaning it's considered primarily a kinetic weapon (so if one isn't available, the autofitter will look for a kinetic weapon to replace it first, *then* a PD weapon).
This is going to be... Interesting to do a D sprite version of every single ship in mods.
Ha - it's optional, btw. The game automatically creates a base (D) hull for everything using the normal sprite. This reminds me, there's a TODO item somewhere to allow for an optional alternate sprite for this auto-generation.
If boarding is gone, are marines gonna just be another commodity for now (a few things current hint at ground/station based ops), or are they kaput entirely?
For now, yeah, just a commodity.
What are the stats on the new D-mods anyhow? I mean, currently, its something like 30-50% reduction in whatever it effects. Guessing a 10-20%?
Glitched Sensor Array is -15% range; Compromised Structure is -25% armor and hull, Comromised Armor/Hull are -33%, it's all along these lines. Notably, the campaign sensor penalty of Degraded Engines is much less now, though it still has -1 burn.
Will you be able to remove the (D) hullmods from Luddic Path ships? If so, I would be willing to spend the credits and turn them into front line ships to hold the enemy back before my main fleet makes it to the middle of the map.
Hah, I was wondering if someone would ask that - yes! You can get a Luddic Path <whatever> with the built-in Safety Overrides and without the Ill-Advised Modifications. Can get a Mudskipper Mk.2 fixed up, too.
I'm 99% sure that boarding is still in the game
Pretty sure I mentioned explicitly that the ship recovery stuff replaces it, but if I didn't: it does
