Just cleared through season 3 and man.. This games a gem. The way you can seamlessly go from stealthing with the mech and plucking ships from a patrol, to juking bullets with the ship and unleashing missiles is so satisfying. My only minor gripe is that I kind of wish that quitting out didn't reset the season.
You can quit out from the Exelios, it's just quitting mid-mission that resets it.