I can store in the MTL file, not just texture mapping, but also Vertice Colour and Alpha settings, by default.
I would like to see this supported by Sansar.
This feature allows for superb blending of colour maps and edge blending between meshes and surfaces. Currently all surfaces that abutt or pass through another, collide with a solid border. Using Alpha Vertice settings, it is easy to blend the surfaces. Very useful for vegetation, water, smoke, clouds, terrains.
Colour mapping using Vertice as opposed to Polygon, is a cheap way of breaking up expanses of a single texture into say height groups, or pathways, that give a natural transition blending between, opposing colours.