Hey there! Your understanding of the state of Nanite is correct.
You’re in an interesting spot, since most folks ask about having to go the other direction (Nanite down to non-Nanite). But I think the answer is the same either way and it sounds like you’ve already got it. What you could do to save yourself the step of batch-converting assets to Nanite later down the line is to enable Nanite on the assets from the beginning but disable Nanite rendering (r.Nanite 0) as part of your DefaultEngine.ini. The big thing to watch out for in your case is that LOD0 will be generated based off the mesh’s Fallback settings, which may not be desirable in your situation since I’m guess you’ll probably want more control over the look of LOD0. For that, you’ll want to set the Source Import Filename in Nanite Settings to be your super-high-res Nanite mesh, then the engine will treat the asset’s normal source file name as LOD0.
Hope that helps, let me know if you’ve got any other questions!