jetBlue would bring a lot of BOS and JFK market share, along with some loyal customers. Alaska would provide a good N/S presence up and down the West Coast.
Only problem is that both airlines are fairly low-wage and pretty solidly low-cost, meaning that their costs would climb a lot if combined with AA.
Similar to the problem with US, another very low-wage airline (although not quite so low-cost).
Even if AA implements the 1113 term sheets, its wages (except the mechanics, Bob) will still be far ahead of US' wages, particularly the pilots and FAs. AA is seeking to reduce its labor costs, but even if successful, it isn't going to become a low-wage or low-cost airliine.