This will come off as dickish, but I don’t care. It needs to be said.
A: Fog is NOT a vdi/remote desktop solution. It is an imaging solution, designed for use on the local lan or a distributed networking environment, not over the public internet. It will not work the way you are asking it to, nor is it designed to. You’re being given a screw driver and trying to use it to hammer nails.
B: Streaming a VHD over HTTP sounds like an ultimate fail to me, due to things like latency and bandwidth involved. If you’re dealing with cheap end user devices already, this is gonna be a nightmare. Take a look at things like LTSP and the like, see how they get around this, and the limitations they have on a LOCAL network, and go from there.
Look at systems like the Guacamole Project on Apache to figure how they’re doing HTML5 gui streaming via VNC/RDP/etc and see if you can build on that. Note, the info there is simply being displayed, not streamed over the internet, and there is still latency involved.
Putting out a request for someone to basically help you develop the entire project you’re trying to build an ‘eco-friendly startup’ on rubs me the wrong way, since so far you’ve offered nothing back to the group nor seem to be in a place, financially or technically, to do so.