I’d definitely prefer not exporting to png considering how terrible it handles alpha channels and rather work with something sensible like targas. Which are not lossy either and typically have well documented handling of alpha channels in the first place.
It’s also very much not a basic Albedo goes here and Normal goes there.
Source one uses a diffuse specular workflow. That means that you’re dealing with a shaded diffuse map and that you aren’t on a PBR workflow either. Regardless of being in PBR Metal or PBR spec, your material construction is vastly different. With the standard workflow you’re looking at reflectivity in the specular and control for the type of reflection (and color tint ) in the exponent map and as such you have to significantly redo the materials to make them actual look decent.
Having a backport of vertexlitgeneric into source 2 would mean this isn’t actually needed. Hence me asking if there is a consideration for this. If not we’ll just have to live with this and re-author the materials and texture maps, but I’d definitely prefer to avoid having to do that.
Honestly the big question is - will old shaders, or at least the important ones, be ported forward.