As someone who has just recently revisited the 1987 TMNT series, I just have to say that if they ever reboot the live action movie franchise for that property, the best change they could and should make to improve it is to make Shredder more like he was in the cartoon. Seriously. A lot of the episodes seem too childish and shrill to me as an adult, but Shredder is terrific because it's clear that the writers frequently gave him lines that they must have known would go over kids' heads probably for their own amusement. As a result, I can notice them now and enjoy the show on a whole new level. And Shredder was just hilarious...the way he bullied his henchmen and obsessed over the turtles so fanatically that it even drove the people he worked with nuts was inspired.
In contrast, the live action 90s movies Shredder was just an almost mute nobody stock villain with no personality and a stupid helmet. That franchise needs a good Shredder in order to thrive. The other big blunder of the live action turtles movies was that they did not highlight the turtles' unique personalities as well as the show did. They were too similar, aside from Michaelangelo sounding more surfer-like and Raphael having a New York accent. It shouldn't have been so hard to differentiate them since they were all basically types (leader, genius, smartass, party animal). The "TMNT"
(2007) movie got that right but had a crushingly boring villain and story.