Geoff Johns said he went with Cyborg as a founding member because he wanted a black hero who represented technology and the future on the team. But thematically speaking, wouldn't Mr. Terrific have fit that role way better than Cyborg?

After Luthor, Terrific embodies cutting-edge science more than anyone in DC and his tone in JSA, the stoic intellectual & moral center, makes him a good fill in for Martian Manhunter as a founding JL member which Cyborg lacked.