Quick update on this. When I saw they added user data to the nodes I figured it would probably be doable now.
Useful for those of us that do product viz with many variations of cmf’s.
Pretty simple setup, add a vray object tag to a null, doesn’t matter if its empty or not; you are just using it to pull data from. Then feed that into your xpresso with your integer user data driving the vray tag object id field. Then use the User Integer node in your material set to VRay_ObjectID. I personally created a Group with ports to have a cleaner setup, you dont have to. Then in that node for each layer you will need to have a Float Arithmetic node with the User Integer plugged into Float A of each node you have. Then you simply set them to Difference and go one value higher than your user data value.
In my case the 0, 1, 2, 3. So 3 Math nodes needed set to 2, 3, 4 so that they correctly activate blend node layers as you click through your user data interface. Then 3 separate outputs from the group node to drive each separate layer. Thats all.
Not the cleanest or smartest setup but works for now 
