Personally I think this is a brilliant idea. I was once in a (v.small not noteworthy) production of JCS and I can say that you really get an intimate feel for all of the characters.. adn that by the end of the run you can do everyone's part. So I think that for 1/2the run david=jesus john=judas and the other half they could switch john=jesus david=judas. I think that would give it even more edge.