Isn't TESS kind of built to do the same thing? Wide field analysis? Presumably it's looking for dimming rather than relative motion, but that seems more like a software issue than a hardware one?
Not exactly. TESS monitors bright objects. It uses actually quite small telescopes (only 10cm aperture or so), but the it has 4 such telescopes and uses very wide fields of view to monitor a large number of stars continuously. To see KBOs/TNOs requires more light gathering power.