Stangri was kind enough to guide me through what was needed, and successfully implemented the required changes to luci-app-advanced-reboot for the MX4200 V1.
I am guessing there is not much difference to the V2, though someone with a V2 will need to provide the required info(See "How to add a new device"). I had to provide some additional info because it was missing from the router commit; you can read through my posts here.