I really like this idea. Actually we had a similar usecase where a customer needed to upload graphics that will be used in the site as collections of assets. So having the grouping of asset collections for example based on a remote path would’ve allowed to just collect those graphics in a way that’s completely transparent / known to the user. And we run some multisite stuff shared over distributions where graphics could be re-used too.
What I’m not so sure about is having the RemoteMedia package, I think I’d rather use this opportunity to transform the Media package into an api package and move the UI stuff to a separate package. This would also be more natural for the usage in Neos. But maybe I overcomplicate the things now 
I’d btw also be interested in helping out