I think it'd work like banks when changing broken bills. You have to have either over 50% or both halves.

If you go to the bank with exactly half a note, they won't give you a new one. Go there with 60% of one and they will.

Go there with the two separate halves, and it'll also work.

So my thinking is resurrecting one half gets rid of the other, or it just doesn't work if there's exactly 50%. But as that would never really happen, one half always has more, so res would only work on that half?

Rules as written, that spell also includes the following two sections, listed before the one highlighted in this post:

You touch a dead creature that has been dead for no more than a century, that didn't die of old age, and that isn't undead. If its soul is free and willing, the target returns to life with all its hit points.

This spell neutralizes any poisons and cures normal diseases afflicting the creature when it died. It doesn't, however, remove magical diseases, curses, and the like; if such effects aren't removed prior to casting the spell, they afflict the target on its return to life.

I think the only gray area would be whether or not the other effects still occur, i.e. if it still makes a body. You can resurrect one half with a soul, but the soul can't be in two places at once, so the other half would either fail completely or be a healthy looking but otherwise dead body.

Casting Simulacrum is cheaper, or you could cast Clone which will give you a spare body when your current one dies.

If you've got 2 000 worth of V S M, I don't see why not