Do you think any substantial perk adjustments would be required to balance this class for the Assault Rifle in lieu of the Bullpup? The Overwatch tree is my main concern, with the Cool Under Pressure + Sentinel + Marauder triple attack.

I dunno, I'd try without any changes - Marine's can get access to a similar setup for ranged rifle overwatch, so I don't think it does anything too groundbreaking - just a different flavor of utility paired with it.

What do you need to do to need Jane Kelly to not need the Proficiency Skirmisher?

Suggestion: Instead of having the class display as "Resistance Leader" why not simply call it the Officer (or Int. Officer) class? Main reason I bring this up it looks messy in the barracks UI.