That's a very good question. I know I have been to churches that have bassists with 5-string basses, and it also makes sense to be prepared as few churches (that I've been to) have a constant set of musicians for more than a few years at a time.
for instruments my church is only running a standard 4 string bass, with drums, electric guitar, electric acoustic guitar, and a keyboard. We may end up adding a cello and some brass instrument soon, but I don't think that will effect the subs.