It would be a good hook for fans (not to mention a treat, a concept album would be amazing), who would all pretty much buy the album anyway, but the everyman is not going to know who the hell Patti is, and won't care.
Meat did his album with Stoney when he was new on the scene and the album was presented as a double act, something that IMHO is not going to work when one person is world famous and the other is known to few.
The Heaven & Hell compilation worked well because both Meat and Bonnie Tyler are very famous names.THe Meat Loaf & Friends worked to a less extent, I think, because Jim Steinman and Ellen Foley are not household names.