Floorless trains, remove most of the tunnel. Add an invertion or 2. The technology and specifics are in place already......and there's land behind to make this viable. Why not????
That would cost so much money, and there just isn't any point in changing Oblivion at this point anymore - and it would take away from its original novelty as well. Also that land there I believe is restricted for what they build on because it's so close to the neighbours. Removing most of the tunnel is easier said than done, it would take a lot of time and money, and Merlin just wouldn't dish that sort of money out just for a little enhancement, they might as well build a new coaster elsewhere.
Basically Oblivion or no Oblivion