I try to train all my VV's in everything also. However, if they have dislikes for some things, it's not always possible. I've had VV's who disliked swimming, so fishing was out, but they could do crops and forage. Some hate rough wood and it's hard to get them to build.
I think it's most worthwhile to train them all to have at least trainee status as Builders. And it's important to have one Master Builder especially during one point in the game, and a Master Scientist.
I've had typhoons wipe out all the stored food. Not good when you have 90 villagers. It's really important then that they can all, or most of them, farm and catch fish.
I do eventually keep them on a certain skill (check it off on the details screen) just because I have this thing that I like them to be Masters of something when they pass away.
Also, a Master Scientist who has maxed out their skill don't accumulate anymore tech points. It's easier to switch them to something else to do if they've had some training in it. :]
I never check 'Breeding'. They do that too well all of their own. I've come back after just 20 minutes to find 6 or more new moms! And some have been quite elderly. Naughty VV's.
