I think acceptance would hinge on what the situation was prior to any merger and whether those groups (shareholders, customers, labor) felt there was a better alternative.
If AS were to ever lose its way financially, I'm sure shareholders would be only to happy for a merger. I would guess employee acceptance would vary by group (do you have to relocate to Atlanta/Chicago/Dallas or not?) and by how seniority rosters were integrated. Probably a fair bit of attrition, but nothing out of the ordinary.
Customers might be a tougher sell for a while at least...but they've been happy to forget a lot of perfectly good defunct airline brands over the years, including a number of AS competitors in Alaska.
So, from where I sit, if it happens, it happens. A lot of feathers would be ruffled, but the uproar would die down eventually.