Perhaps, this is a sign that Parker/AWA is wielding some influence, though that's something they would have to be very careful about legally. If there is enough money to pull the merger off and there is enough for US to make it to the altar, then Parker may recognize the value of keeping MAA as a subsidiary/division that's already up and running with low costs. Starting next year, it will probably be the best and easiest way to pull in some E190s to replace all of these outgoing 737s w/o going to war with labor.
In the long run, it's probably more profitable for the new UAIR to keep this in-house, as well. The only reason to sell these aircraft and the slots that have been discussed is for a quick infusion of cash. If UAIR can limp along without it, then they will be better off to find a way out of this deal - even if they have to eat some fines from Embraer while getting their ducks in a row for the merger.
Some may see this as a typical "bad move" by CCY; personally, this seems to me like someone is actually thinking beyond the current crisis and trying to put the brakes on a deal that ONLY makes sense if they're desperate for cash in the short term.