I can kind of see the utility. However I also think it’s a rabbit hole, feature wise. Like, if we expose files over HTTP, we should probably have authentication, right? And rate limiting? MIME type detection? Download quotas? One time access tokens? Image gallery generators? Video streaming plugins…? SOAP? Where do we draw the line? Is this still Syncthing we’re talking about, or something else?
On the flip side, you have things like Freehold, which I haven’t tested at all but looks like it might fullfil the initial requirements, even includes some sort of upload/sync client of it’s own (!) and is also just a single binary to download and run.
Freehold is a webserver that you can host on anything from a multi-core VPS to a Rasberry Pi. Running the webserver is as simple as starting starting up the freehold executable. Once running the freehold instance exposes a simple REST API for uploading files and managing them. There is also a built-in datastore API that allows for storing any other type of data you need.