There's periodic talk amongst AS FFers that a platinum level would be a welcome change to the AS plan. MVPG upgrades on an increasing number of flights are become harder to score, partly due (IMO) to AS' favorable pricing of purchased F tickets on many of their routes, e.g. west coast N/S mainline.

AS' partner relationships with so many ST members (albeit decreasing in number with the NW/DL merger and CO's defection) would be the main sticking point. There are, of course, partnerships between current OW members and members of other alliances, like QF/AZ or CX/AF, even QF/SK, so possibly not insurmountable, at least on an interim basis.