Q80
Can effects that increase size or increase the damage of naturals weapons by a size (Enlarge Person, Improved Natural Attack, Sharptooth, etc) stack with the effects of Greater Mighty Wallop to increase the damage of a natural weapon beyond Colossal, or will the extra size increases of Greater Mighty Wallop start to overlap with other effects?
Whether or not it's possible to increase damage beyond colossal is debatable, but Greater Mighty Wallop is very specific about not being able to boost a weapon's damage beyond colossal. Regular Mighty Wallop, however, does not have that clause, thus returning its status to debatable.
So then it is up to interpretation?
Sort of...
Size categories above colossal were made (in reference to specific entities which fit them, though no rules limit them to just those entities) and tables with quite easy to see patterns exist to properly track damage increasing along with size, but nothing explicitly states that you can
increase to a size above colossal, and those tables all cap out at colossal size.
Logically there's no reason it wouldn't be allowed, as all the tools to make it happen are present and not limited, but many believe that since it is never explicitly spelled out that it cannot be done.