Just my opinion.
If you were to loan your guitar to someone who doesn't know how to play, it will sound bleh.. Same thing applies to someone who doesn't know how to play keyboard, better yet, someone who doesn't know how to play a bass line on a keyboard. With that said, don't go chasing sounds, you can get lost in that rabbit hole. As mentioned, Dimension has some sounds that should do well. The Mu50 should also have some good sounds. So, the key is practice.
However, I agree with the others, for traditional bass sounds, it's hard to beat the real thing.
As far as drum replacements go, drumagog is a good suggestion. However, if we're just talking about a hit here or there, it's probably just as easy to cut & past the sample where you need it. Or, you & your drummer friend can spend a little time learning how to tune the drum, mic the drum, track the drum & process the drum to get the sound you're looking for. I think that will help you out in the long run.
V-Vocal vs Melodyne.... Melodyne is deep & it's expensive. Play around with V-Vocal & find out if it can do what you need it to do. Melodyne does a lot of extra stuff, that can come in real handy, but a foundation.. a solid foundation in V-Vocal will help you get the most out of it.