I see. i don’t understand what your problem is. sounds like you have a choice to make.
i personally wouldn’t try to optimize for drawcalls to the level that it creates issues with the workflow.
afaik if you are using different materials then there’s no such thing as “merge draw calls together”. each material is a draw-call. afaik. even on nanite.
in fact in nanite meshes that are different but have the same material have some optimizations and trigger less draw calls.
there’s also instance meshes, hsim, and auto instancing which i think you might be aware of, but good to remind them for other readers.
that does not seem to be an option from my pov. that’s why i meant you have a choice and not a problem. but i don’t know a ton about uv mapping in ue, i’d assume you know more than i do.
i have an idea though.