How 'bout NONE until the unsculpted mechs have been done first.
Ostwar and Von Rohrs come to mind, probably others I'm overlooking at the moment.
After that, I think the Gunslinger needs a look...but I shudder to think what might happen along the lines of the Orion, Atlas, and Enforcer. :'(
Some proper Charger variants would be cool. Like the CGR-1A9 or CGR-3K (practically the same thing), CGR-SB or perhaps the CGR-1X1? You could even start with the original minis and work mods from there similar to the Grasshopper that was "updated" recently and turned out very nice.