Hello,
What I did was that I isolated Root Storage from Workspaces (you can't reach storage from Network Perspective and Authentication Perspective) - it is ugly but it works.

What you could try is to do that via API (like update metastore to NULL storage root) - sometimes I was able to achieve more using API then UI (even not documented things ) .

I would avoid migrating entire metastore unless your entire UC is base on code (all Create statement for UC Obejcts)