There already is a 1:1 in the ASA to swap out 200's for 70/70+ seaters. Buying us doesn't necessarily void the contract on -200's. I would have to look at the fine print but it wouldn't seem financially positive to buy a regional (at least not pinnacle). NW has bought regionals that were on their last leg (mostly by their doing) and built them for an IPO- look at Pinnacle (was Express 1). Bought em at the bottom, built them up with 200's and got rid of the saabs- then sold them for a nice profit and got rid of the financial burden. I am not a fortune teller or have any "inside knowledge" but it appears NW is/was doing the same thing with Mesaba and Compass. Time will tell but there is no reason or scenario I can think of that would justify the purchase of pinnacle.
It wouldn't void the leases but it would void your long-term ASA or atleast make it easier to void I would think. I'm no lawyer or businessman so I really can't say that with any certainty haha