Yeah, I see a Megaish coaster as well. The problem is, Megas take up loads and loads of space. You need a large rectangular area for each hill you want to put in (most notably, the lift hill), a large area for each turn (the earlier in the layout, the larger), and obviously access for construction equipment all over the plot (so building it along the perimeter of the park is out of the question). Where could you fit one?
^Also, not going to happen. The closest you get is Maverick, whose focus is on terrain-hugging and quick maneuvers, not lots of inversions or big hills. This focus enables it to do both to some extent. Also, I think rolls require a wildly different set of trains (connections between cars, different restraints, seats, etc), so slapping an inversion on a Mega would require lots of hassle for little gain. I mean, if you have a Mega, you would rake in on the guests without an inversion anyway.