My view all along is that Peel were looking to make money out of developing the surplus land at MME, same way as they have at LPL. It would be a lot easier for them to get what they want out of the LA's in terms of planning etc, if this is tied into a viable MME.
I think they will find (or they should find) it a lot harder to develop the MME land once the airport is shut - it then just becomes another brown field site (again, is Teesside short of these?).
Unfortunately times change, bmiBaby bombed out, Globespan bombed out and now nobody else is interested and the losses have become unsustainable.
Like Onion says - time for plan B. Cut your losses and play the long game.