First off, I have to thank Peter Hopey for providing the inspiration that led me to make this conclusion. After reading his article regarding Bill Goldberg's intentions to return to the WWE in WrestleMania, I have to believe that he must be the proverbial man behind the curtain (or in this case, laptop) on Raw.
It makes good sense if we think about the setups provided recently. On the 8/16 Raw, the GM e-mailed Michael Cole to let us know that Bret Hart was going to be replaced by a different competitor in his match against Justin Gabriel. Not only was Hart replaced, but the GM continued to let us know his distaste for the Hitman.
Does this clinch Goldberg as the GM? By all means no, but the comments read by Cole indicate somebody who has enough history with Bret to want to screw him over. Bill Goldberg certainly didn't have much in the win column against Hart, so that helps his case.
As it stands, a Goldberg return has no motivation other than him wanting to return. The GM storyline would be a perfect vehicle allowing such a return, seeing as how the WWE appears to be stalling with the Mystery GM. Does it make any less sense than any other name on the roster? The WWE has a bad habit of pulling out the Wheel O' Superstars and throwing darts to determine matchups, so why not Bill? Having him as the Mystery GM would allow the WWE to build a storyline without him even needing to be present until the Big Reveal. Currently, the Raw GM is almost completely neutral. Goldberg always was a hard read to tell if he was heel or face sometimes (usually whatever opponent he face would indicate that), so the ambiguity fits.
The big payoff, it seems, would be a pairing of him against Cena at WrestleMania. It would be a perfect setup if Cena were to continue to egg on the faceless GM and call him out, only to find Goldberg waiting there to man up.
The only problem is that VKM is running things. Lately he seems content to rest the fate of his company on brand name alone, and the rest of the candidates are underwhelming enough to fit his current creative plan (excluding Dwayne Johnson - he'd rule). Goldberg provides some oomph to an otherwise dreary cast of seat-fillers for the GM role. He may not be the biggest star for the job, but at least it would be somewhat unexpected to see him in the role, and unexpected gets people tuning in, and isn't that the ultimate idea behind Wrestlemania?