Yeah, a large javanicus wouldn't really bother eating a tiny little damsel. They want to get some bigger food, they want snappers and groupers and the like, all bigger fish. They're not going to exert all the energy to eat one tiny little fish. Damselfish or a school of chromis would be a sweet combination to make the tank a bit more interesting, and yes you could keep some cleaner shrimp in there. There's nothing more awesome than seeing a monster moray with its mouth open and cleaner wrasses and shrimp eating away the dead flesh in between its teeth. Awesome site to seeA moray with a huge school of damsel species look awesome too hehehe.
I love to watch my cleaning shrimp busy cleaning the moray and damsels at their cleaning station. My moray do enjoy a small snack damsel from time to time when that damsel run direct into it nose/mouth or badly injured from fighting with each other. Oddly, my rock beauty angel still live happily with my moray when all other bigger tank mates already become moray food.