On the tourist roads I've visited, a radio in the cab isn't always safety oriented. It's a lazy form of communication, 168 could be restored without a radio and therefore crews could use hand signals which would be more historic and more sophisticated. Something I've noticed is very rare on the "historic" C&TS. It would be pretty neat to see a historic period train set without a blaring speaker heard from the cab like the rest of the locomotives on that line.
For real safety reasons, I assume a second water glass will have to be fitted to meet current regulations.
-Maury