The only way AA builds up SJC service is if they buy AS. Then there would be a reasonable case to run some planes SEA/PDX-SJC-(AA hub), plus they could use QX Q400s instead of RJs on SJC-LAX, on top of AS's current service. It would be good for utilization.

That being said, I don't think AA is buying AS anytime soon (and there's a sad history involved where West Coast airlines and/or AA purchases get turned into empty gates and beer cans- WA, TW, QQ and so on).