Roadsters of that era left the factory with the old style hydraulic pressure switch, these tended to fail because of the crap quality of switches (not MMC's fault almost all the current makes are rubbish) the longest lasting I've found are Intermotor brand.
Lot's of owners added a simple relay to reduce the load the switch contacts take & this generally works well, but worth carrying a spare hydraulic sw if you're doing long tours, as they can be changed roadside without needing to bleed the brakes if you are confident & don't dawdle with the spanner
Relays have their place but would favour a quality hydraulic or direct pedal operated switch, underrated current wise for the task. The extra wiring and possibly poor location of relay adds complexity and potential unreliability.
Note also having LED brake lights as well as generally being brighter puts far less current load on switch.
