Just saw this thread and agree this would be a great idea.

Not everyone (probably not even most) book all their airline alliance tickets through their "home" airline and probably even fewer through that airline's own elite line. Frankly I don't think that NW's elite line would be interested in booking a revenue ticket for me on their competitor/cooperators within SkyTeam. If DL does that and it's worth the booking fees to PMMMDL, then more power to you.

But if I'm flying DL, I'm probably booking on delta.com. Let's not even get into how Skyteam-unfriendly delta.com is. I should as a Skyteam elite, be able to call into the same phone queue as does a Medallion member. Same if I'm flying some other Skyteam airline.

This would be a great benefit and would be a big differentiator for Skyteam from oneworld or *A. Skyteam promotes itself as "caring more about you" and this would be very customer-centric.