How to safely Change Location Upload folder and folder structure for Excisting MultiSite

I have a question for where I can't find a complete answer. The case is we have a multisite and want to change the upload location preferably to a subdomain. In this subdomain we want to have a folderstructure without separating in dates. This is because in having a Woocommerce shop we change product information regurarly and don't want images uploaded every time to a new month folder. I read that I can set the upload location in the config file, but how about changing all the existing paths to the new folder. Some did this by using WP All Migrate Plugin. As we have that this plugin in our multisite, would this mean exporting the subsites, deleting them and adding them again to the multisite. Do I change the default location for the uploads in the permalinks of the subsite to the subdomain for the uploads before exporting this or do you (WPMU support) has another (better) solution. In any case the database entries has to be rewritten to point to the correct uploads location. By the way our WP install isn't in the root but in the Public_HTML folder on our Siteground hosting.

Any help/insight in this is very appreciated,

Tom
WP Rookie