Until someone brings out little two or four drive NVMe enclosures that fits exactly under the Mac Mini with a Thunderbolt bridge/plug that doesn't snag cables, because we all know Apple can't resist gauging buyers by refusing to include two easy to access M.2 bays on the underside.

I can't imagine anyone but Apple shareholders drooling at the taught of overpriced soldered memory would prefer a smaller Mac Mini case if ~0.5" more height would get you M.2 bays for storage.