For the limiting firmware, there is a 14g under development now that besides having several features and enhancements for everyone includes some that should specifically help your run of boards. The slow ramp to help heat the boards will be more efficient and will be active at the time instead of just on the startup. As well, the board will drop to idle voltage (0.9V) if there is no work and then slowly ramp back up. That should help prevent resets in the case where the board cools due to lack of work and then starts back up.
The maximum voltage will also be configurable through a z command, so a user can tweak that parameter on their own rather than having different firmwares for different voltage limits.