Chessie's ground isn't the most stable, look at the state of some of the pathways and you can see it... Slip sliding away, so digging is pretty much out of the question...
Can only imagine what might have been if Tussauds hadn't hit the brick wall of the council prior to purchasing Towers...
Thing is as well, much like Lego's issues, there's the traffic issue to consider, which is bloody awful at the best of times... It's not simply down to height and noise, and probably not helped with the relationships our parks seem to have with councils (as in, everyone hates each other)... But Chessie simply doesn't have the sufficient infrastructure available to it to support a major modern park at the current time, which is evidence of it's bad treatment under DIC...
Merlin's stuff is short term at more than just Chessie... That much is clear...