Purge missions could be improved with the addition of markers for remaining enemies, and a tweak to the map generation to prevent looping/branching paths. Backtracking during purge missions can get pretty ridiculous depending on how the map was generated. A single continuous path would work rather well for this mission type.
Shift does not work very well as a cover button, it's awkward to press with the fingers resting on the 1,2,3,4 keys. Furthermore, I think that the character should move towards the nearest piece of cover when Shift is held, several times I found myself standing just outside of cover and not actually taking cover. A lot of objects don't count as cover when they look like they should.
Looking forward to seeing how this progresses.