I'm not sure if I've missed something here, but I don't think anybody has suggested selling Bellamy and Nelsen and probabaly even MGP.
Personally, I think MGP could be replaced, maybe even for free with Peter, and we would still have real money to play with in the transfer market. Imagine what we could do with, say, 8 million...
However, I agree that he is a fans favourite, and his exit could cause real disillusion. He is also extremely influential, and by leaving could upset the balance of a winning team.
As for Bellamy and Nelsen. Well they are probably our best and most influential players. Bellamy on his own I wouldn't sell for 20 million and I don't think any offer for Nelsen would be large enough.