I do a fair amount of M&A in my line of work as a corporate attorney. Companies that are acquired remain "intact" as distinct corporate entities all the time as wholly-owned subsidiaries of the buyer. That doesn't mean the parent company doesn't control them via complete stock ownership and thereby the board of directors, which together have complete power over the company and its management. The fact of the matter is that if Gibson really did buy Mesa, they can do whatever the hell they want to/with them, and whatever spin is being put on the situation now is meaningless. I hope things don't change, but if Mesa was actually acquired, my guess is that, absent Gibson agreeing to some very non-market and atypical covenants, Mesa isn't steering the ship in any meaningful capacity.
That being said, given the status of Mesa, I think Gibson would be stupid to interfere with what they're doing. They should really just leverage economies of scale/distribution power, and let Mesa do its thing so long as they continue to stay afloat.