It would be nice to see AS in oneworld. It would cover some of the gaps around North America.
Joining oneworld wouldn't jeopardize relationships with non oneworld members unless that other airline decided to jeopardize it. Many oneworld members have relationships outside the alliance.
AS is part of the Global Explorer ticket (mileage based version of xONEx), so it wouldn't be that much more to join the alliance. Many other airlines on the xGLOBnn later joined.