Mecha rules? Good idea. I have never been into the Battletech scene, but there must be something to it, considering all the fans worldwide.
The more Polyhedron strays from the ever-popular Tolkien/Howard/Lieber mode of roleplaying, the more I like it.
If you felt really cocky, Erik...how about a giant-sized issue with superhero rules? That will be, I think, the greatest challenge for the d20 system. Use this as a test run, and then maybe the Marvel or DC license will come (if Wizards even wants to screw with that a third time --- but d20 Marvel, if it's even halfway good, would sell like hotcakes).