I've read most of the earlier posts.
I've made my decision.
A guy with a prosthetic arm IMHO should not be flying a commercial pax flight.
Flying is a tactile operation first and foremost, tends to be more so during the T/O and landing phases...
etc...
Best to the pilot, but, in all reasonable risk assessment scenarios...
His medic sign off better have good insurance... and may rethink his renewal...