Remember back in the 70's, when the Mustang and the Pinto were the same car with different sheet metal?
I'd say there would be a likelihood of a variant to compete with the new Dodge Magnum.... I don't know if it should be badged as a mustang, but to share the basic underlying platform, and only change the sheetmetal and layout might not be a bad move.
Magnum seems to have done well for dodge, and cross over is in... why not a Ford sporty version of one?
Well, if Chevy can make a Me-Too Cruiser, Ford can make a Me-Too Wagon
(following the Magnum concept).