My team has built a two motor flywheel without a ratchet. We have a ratchet prototype and ready to be used. We found the brake type coast in late October and have been using that since the construction of the flywheel (roughly mid-October). We have been to one competition and have done many tests on the flywheel without a ratchet.
We are now in the process of designing and building our second iteration of our flywheel. We had friction problems that needed to be resolved. The old gear ratio was a 11.66 increase in RPM, 200 motor output to 2333 flywheel output. Anyway, we have never had a problem with the motors heating up to the point where they stop working. They do heat up, within reason. Brake type coast works well in a match.
The only situation i can see a ratchet having a substantial advantage is when the flywheel is spinning at the end of a match, the match is ended, and power goes back into the motors. At this point, the robot is "disabled" and not performing any of its usual functions. The motors are not performing the coast brake type and will be forced to accept the power transferred from the flywheel.
Hope this helps.