I don't know if Transformers would really work as minimates. TFs are supposed to be big and bulky. I think if they were made, they would be more like the current Robot Heroes. It would be cool to have the humans in Transformers as minis: Spike, Sparkplug, Carly, Daniel, Chip Chase...Shia Lebouf, etc.
But if DST could somehow latch onto Star Wars, that would be all of the "major" licenses covered, really. GI Joe and He-man would be cool, but licensing from toy company to toy company would be something that the corporate bigwigs at Hasbro and Mattel would never go for.