I don't think Rutgers particularly wants him back; he made a lot of enemies here. I don't think he is likely to want to come back to basically try to repeat his earlier success here --- he looks bad if he fails, and it's ho-hum "been there, done that.' if he succeeds. Actually making Rutgers football much better than he left it would be a Herculean task given that there is no way Rutgers is going to spend what schools like Ohio State and Michigan do.
Even assuming the parties want to make a deal, there's the problem of salary. It's going to be hard enough for Rutgers to persuade itself to help to fund Ash's buyout; it is impossible for me to believe that the money is going to be there to pay what Schiano will want, even if Schiano only wants what Ash is now making. The only way the money is there is if the donors can be persuaded to make a massive effort.
So, in summary, it is not realistic because, in no particular order:
A) We won't have the money
B) GS is not interested
C) GS made enemies here (presumably among those who would make such a decision or would influence those making the decision)
So, this become a realistic scenario if we find:
1) There is interest on our end
2) There is interest on GS' end
3) We somehow find the money
I believe that we SHOULD have interest. And people have said there was some interest by GS last time around... so it comes down to money.
I have said elsewhere that once you start looking around or above 4M we should open the field.. that kind of money should attract serious talent (but I do not think that can happen here.. not until we get full share from B10 anyway). I have not looked into who that might be.. but if if you can get GS at 3.5M or lower.. jump on that. And as for his demands for the program and control.. do what BM did.. TRUST HIM.