I'm shooting something at the moment. And I have a scene where, I have a completely white material covering the back wall. Now I want that back wall to be completely brilliantly lit, but yet I also want shadows without the subject looking like the lighting has had a harsh effect.

So basically, if theres no pracitcal way of having soft skin tone with the background being seperately lit and not getting rid of the shadows, which would be the easiest and most successful looking in post? Would it be better to blast the wall with the light I need and add realistic looking shadows later on that follow the subject as he or she moves, or would be easier to keep the shadows and make the whole the back wall look like it has light shining on it on post?

I don't understand at all, but if you were to correctly expose you could:
Luma Key the backdrop out completely, and do what ever you want.
or
Adjust the levels, to make the white nice and white.
or
Add a glow, if that is what you are getting at.

All this is best to do in after effects, but final cut has a glow I think. I don't know what you're doing, but these effects are probably what you're looking for.