Possible? My guess is, probably not. I suspect the user interface is tied to the ROMs inside the new iPods, so the new interface will only work with the new ROMs.
In theory, if you could get your hands on the new ROMs, there might be a way to swap them out with, say, the 5G Video iPods. But getting those ROMs is nearly impossible. I suspect Apple made it very difficult to hack around this.
Realistically, I think you're better off just buying the new units.