hi Ken,
As you probably know, it can be done inside style or as multipad. I always prefer to have everything inside style (means, in a single file), which in this case is not a problem, because music is not busy and would probably fill only few channels.
The only reason why I would decide for multipad is, if I would plan to use the same padding (or effect) for other styles in future. But even then, it's easy to copy content from one style to another and keep style independent.
PS: About picking a voice that replicates the singing... is usually very problematic, because it's not only about what sounds nice (to the music). The thing is, a singer always sings emotionally and it's very difficult to find a voice that can transfer these emotions. I mean, let's face it: the song you wish to make style for, is actually good mainly because of the singing. And if you decide for wrong leading voice, the whole result can be totally different than you imagined.
I'm in similar situation right now... I made a style (only Main A variation so far) and I'm trying to find an instrument (voice) that could replicate female singer, but didn't found it yet. Will see how it ends... if ever.
Just sharing my thoughts,
Bogdan