Seek investment capital to buy out the group from the councils, including the land freehold (I know that'll be expensive but it'll reduce costs, because the ground rent is artificially high as the councils/freeholders treat it as extra dividend. Also a disproportionate amount of it goes straight to C of Mcr, not the other nine).
In order for there to be a purchase there needs to be a willing vendor. I strongly suspect that AGMA (all the GM councils) would not wish to sell a source of revenue unless so directed by the district auditor on grounds of poor return.
I have no idea of the distribution of profits but the apparent disproportionality referred to may simply be a reflection of the proportionate holding each council has, Manchester 55% the other nine 5% each.