They've finished outside the CL places 5 of the last 10 seasons since Fergie retired, they might have a bad season or two but will end up having a good season at some point and getting back in it, which will be even easier now as there will always be the possibility of 5th getting a CL spot. There worst season since Fergie is equaled to our best in the same period, excluding this season. Their demise is overrated.
I'm no expert on FFP, but if he has £15m of amortized value left, and we sell him for say £20m that would mean an FFP profit of £5m? Doesn't that give us £25m to work with under FFP? We can easily sign a younger 4th choice CB on much less wages for that, it makes perfect financial sense.
I could see this happening. The League Cup should be retained though. Isn't the League Cup organised by the EFL anyway, of which the PL are separate? So, The League Cup for EFL teams and a Premier League Cup for PL teams, which would have various matches played in different countries.