Interestingly, the government's Competition and Marketing Authority (CMA) has been having similar thoughts :-
"73. The removal of the grandfathered rights and auctioning of slots should increase market efficiency and allow for greater competition between airlines. Airlines would be able to compete to access slots periodically, which will lead to slots being used by the airlines that can use them most efficiently. New entrants would be able to increase their slot concentration quickly and be able to provide more competition to incumbent airlines on particular routes. The result of which should lead to better consumer outcomes, as airlines have a greater incentive to optimise their investment and encourage greater innovation in the subsequent use of slots. "
This from their advice to the DfT,
https://assets.publishing.service.go...port-slots.pdf
The key would be future auctioning of slots, sales between operators allowed, but otherwise retained on a Use it Or Lose It basis. The words Hens, Foxes, And Chicken Coops spring to mind...