Increasing the levels to 80 on forgotten attack worlds presented a major problem to those that were near the centre as the levels of the forgotten went from 65 to high 70's and 80. They got slaughtered!
Similarly increasing the levels 80 on morale worlds presented different problems with players finding themselves in areas where they had much more difficulty as the forgotten levels jumped but their corresponding offence levels didn't.
The only places where a level 80 increase is less problematic is the very old numbered worlds (where very few players still spend money) and even those found a problem with killing the bases that regenerated at a much higher level.
The only worlds with level 80 that are successful are those where it starts at 80, IMHO.