Quote - Question for the modellers here:

Say I have a clothing mesh I made for V4. How hard is it to take that same mesh and resculpt it to Anastasia? Is it easier to start over from scratch?

Not necessarily easier to start from scratch.  It really depends on how closely body shapes match.

I would probably save the basic, low poly dress and use that for a different model, rather than starting from scratch completely.

How easy/hard a conversion is can probably be compared to how well either of the conversion programs (Wardrobe Wizard/Crossdresser) work on a specific model for the base conversion (not including JCMs, etc.).