I don't think there is any reason they couldn't make a Luger 4.5mm CO2 with blowback ( or whatever you call the rising/falling toggle action): there is already an airsoft version.
Personally I would love to have a CO2 4.5mm blowback Mauser C96 (airsoft version already in existence). I have emailed Cybergun and asked them if they have any plans to make one. Probably being wildly optimistic. Anybody else fancy one of these? If you do, email Cybergun too.