I agree. We'd have to pay him a 'loyalty bonus' that would get him off our books and onto somebody else's.
We should be doing this for all of the sub-par players whose wages are crippling the club. Eg Souttar, Ward, Iversen, Kristiansen, Soumare, Daka. And we should have done it a long time ago to many, many more.
I'd much rather directly pay Daka a good chunk of the transfer fee we'd receive for him to get him to accept a lower contract elsewhere. Not unrealistic to think we could get somebody to pay us a fee equal to or more than the ~£8m we owe him.
Otherwise we're just throwing good money after bad, continuing to wrack up debts and keeping crap players until they inevitably leave on a free.