Hate AS much? AS has a far greater International reach than B6. While they don't currently, they have served the Russian Far East, they have been serving both Canada & Mexico for decades, nothing B6 has done. Now B6 flies the Caribbean, Central & the Northern part of South America.
AS last served Russia in the Clinton administration, they fly to 15 international destinations in 3 countries compared to B6 with 33 destinations in over a dozen countries. I'm not entirely sure why you think Alaska "has a far greater International reach".
AS would be the aggressor in a pitch to obtain B6, they would lose the JetBlue name, integrate it all into a much larger Alsska & eskimos would be flying from Europe to Hawaii & Alaska to South America.
...Probably, but it could be an HP-US situation where Alaska buys B6 and uses the B6 name. It would likely depend on the amount of name recognition and perception of each airline.
In short if AS buys B6, AAG deals with Embraer on replacing all the current B6 E-190's in exchange for more E-175ER's. The older Airbuses that could go, would go ASAP. Again AAG will be cutting underperforming services. Depending on age & time left on the lease terms, AS may decide to poark old Airbus aircraft & only refurbish those they own or are still filled with life on their contract.
Speaking of contracts, I wonder how thrilled the pilots union would be to hear that their flying would be farmed out to regional carriers. I would expect that to go over like a lead balloon.
I could imagine more than a dozen cities would be chopped, but I'd also expect AAG to fill in some places with adds in LAX, FLL, BOS, JFK, SFO, PDX, SEA & ANC. When you overlap their route maps, it is incredibly complimentary route map. While, as others have stated, there are fewer destinations in the middle & that's true with many carriers.
With which large carriers? They not only have a decent amount of 'destinations in the middle, but they all have multiple mid-continent hubs. AA has ORD/DFW, UA has ORD/DEN/IAH, DL has MSP/DTW/SLC. WN has DEN/MDW/DAL/HOU/etc.
JFK is the closest thing to a geographic connecting hub, and that's an incredibly low bar to climb. Anyone not going all the way to a coast would require backtracking to make a connection in almost all instances.
To sum up: This is would be a dumb acquisition, I think a codesharing agreement to start would be MUCH more beneficial to see how well their passengers would play together and see if there is any potential complementary city-pairs.