I hadn't thought of using Redrum as a click, but that seems like a really simple workaround for those that need it. I have had zero issues with using the stock click. it's a click, which is something that is by definition not going to end up in the song, so I don't really understand the idea of expecting your click to be "musical". not hard on the ears I understand, but "musical" just seems like an odd requirement to me. that said, I would actually think using a tone would be less musical, since it could be out of key with the rest of what's going on, whereas the stock sound is more tonally neutral.
at any rate though, I can't see that it would be hard to implement a selection of click options, and it would keep users from needing to try using Redrum if the stock click doesn't really suit their needs, so... why not?