As everyone has said, design wasn't really as big a problem as getting a good story.
1 and 3 - I thought they WERE photorealistic. That was part of the problem. After all, real turtles...
I would be interested in seeing something reptilian and scaly, like this...
This look did earn an Oscar after all.
2 - This point stands. It's worth noting that the 2016 had the Turtles wear less stuff on their bodies, and looked the better for it (as did Bebop and Rocksteady and Krang, who turned out better than their concept art).
3 - The Turtles being huge and muscular was in the 87 and 2003 cartoons, it was from the 2012 cartoon and the IDW comics that the "youthful medium-size" look got prominence.