So the two approaches I see are to either push PBR, or non-PBR information. The former is limited to the number of things you can ultimately push. No dedicated metal, AO, etc, etc. You would still want to track where what ‘layers’, parts, rock/dirt/etc are to be able to append that info on the post/read-RVT-side. There is a Mask channel for this, which can help but since you are already dipping into tracking-alphas, I ditched the PBR altogether and was able to use the remaining channels to track a decent number of things. 5 channels (RGB, Spec, Rough), 6 if you use the mask. Using the Normal channel for the vertex-normal-ws of the landscape, I can use that on the other side in a variety of ways (particularly triplanar mapping).
As well, since you are putting the texture-samples for the draw on the read-side, you can scale them to whatever texel-density you want/need, and aren’t limited by the fidelity of the RVT data-object.
The trade-off is that to be able to blend meshes with a landscape, you have to either use a dithered-solution, or redo the maths that draw the landscape, but in the mesh; there is no PBR to sample from in the RVT.
It CAN work depending on the approach, but depending on the results you want with the mesh, be less or more costly.