Can specular/glossiness textures be exported from Substance Designer in a way that would work with Vray/Arnold/Clarisse? I can see the options when exporting from Painter, but in Designer specular/glossiness template says "This workflow is not compatible with offline renderers such as Vray or Arnold." Is there a…
it working in other applications is no guarantee that the UVs aren't flipped - marmoset certainly handles it correctly. I don't personally know if arnold/maya does
Arnold would be able to do this. Arnold isn't a third party rendering engine anymore - it's the default maya one. You could also use mentalray, renderman, or vray.