(FUSE). Preferably without admin rights. An example would be sshfs, maybe via MSYS?
There is a FUSE compatibility layer for the Windows File System Proxy (winfsp).
This project seems to be live (as of 2019) - although it looks to be almost entirely a 1-developer show.
Code is hosted on github under GPLv3 - "If you find the constraints of the GPLv3 too onerous, a commercial license is also available."
Someone in my office has got winfsp running, but not using the FUSE compatibility layer.
As far as I understand, Windows doesn't ship with anything that would let you define your own filesystem without adding some code to the kernel (i.e., a driver). So you would need admin rights.
In 2010 The FUSE FAQ mention a few potential alternatives, but they all looked like vaporware except for Dokan. Dokan has been abandoned but some forks live on: Dokanx, Dokany, and more as well as at least two .NET bindings. Dokany has an SSHFS component.
When MS introduced GVFS they created a new filter driver that's more or less FUSE-alike
GVFS relies on a new Windows filter driver (the moral equivalent of the FUSE driver in Linux) and we’ve worked with the Windows team to make an early drop of that available so you can try GVFS.
I've seen links to this Windows library Callback File System that seems to be a commercial port of FUSE. I haven't tried it though. And it seems to be $2,500+ for commercial usage.