As much as I liked Russell when he was with us, I think DerBomber has pretty much summed up how I feel about this.
Aberdeen FC can not afford to take the financial risk that he is actually available for even 50% of the time. Pay as you play deal would be ideal, but anything other than that would be crazy given the state of our finances.
Your statement of "would at worst be available for 50% of the time" has no basis whatsoever other than your own optimism, as he hasn't been available 50% of the time down south. And if he has, he still hasn't played 50% of the games, in fact nowhere near it which raises questions of sharpness, not to mention the impact so many bad injuries have taken on his ability and confidence.
Mark McGhee will get the fans onside by winning matches. Simple as that really.