Unfortunetly the link to the feature request site denies me access.
My request is as follows:
Allow weight painting to control texture placement.
Feature Request: Texture control via painting
Moderators: jesterKing, stiv
One of the developers working on the material nodes has said he would be putting in a node to allow access to vertex colors. That would allow you to use each channel (rgb) separately as masks or just plain texture channels. It would also work with a minor mod (IMHO) for weight paints, too.
Just wait for it.
Just wait for it.