Other than technical coolness, what would be the advantage of it? From just a user perspective (i.e. forget technical stuff) what reason would I have to want that?
You're talking technological "wowness", but bring it back to "in the trenches" "daily usage" terms for a typical user: why should he/she care?
To investigate how people use TiddlyWiki, what choices they make, and why, you will get more responses over at TiddlyTalk. It has become the fan-favourite.
I store all of my personal TiddlyWiki instances on Google Drive. TiddlyWiki aside, if I have no access to the internet, any computer is useless to me.
However, since I have offline access to my files on Google Drive, my Chromebook isn't quite the brick folk would think it is ...
Most important to me is to have access to all of my things in Google Drive from any connected device anywhere.
Having my TiddlyWiki instances tied to databases of a web browser on some machine? Nope, not for me. Unless whatever you come up with has auto-syn with the cloud, I won't be using it.
A big draw to single-file TiddlyWiki: 10 years from now, however long a TiddlyWiki has gathered dust, I can open it and everything will be right thre.
In this case, TiddlyWiki instances I've setup in virtual machines using cloud services.
So that I can take advantage of all the goodness that is nodejs TiddlyWiki. All of them tiddlers sitting in individual text files, right where I want them.
Although what you describe would be, I think, of no interest to me here, the ability to have these TiddlyWiki instances able to access databases on these servers, so that the TiddlyWiki instances could have access to data coming from other systems? That would get my attention.