Before I read the linked page I assumed this was a rant about using MS Office with files on your local filesystem. Although that would be titled "How Hard is it to Save a File?"
EC2 is pricey if it's all you're getting from AWS. If you have wierd requirements, colo may be a good option. Otherwise, just get a VPS or 3 and be done with it. You'll get a virtual KVM that lets you boot it off an ISO and set it up the way you want.
Vultr, DigitalOcean, Linode, ... are long established VPS players.
I'm cheap and buy VPSes off deals on lowendtalk.com. e.g. my backups are on a VPS with 3TB disk, 2GB RAM, 1 vCPU, USD7/mo. I suspect your USD80/mo budget would stretch to something amazing, by comparison.
Sharing filesystems is hard when you make users do it in advance.
I was thinking of the server end of an ffmpeg-over-ip system bringing up a FUSE filesystem backed by something similar to your VFS-served-by-the-client. Combine that either with argument rewriting, or chrooting into the FUSE filesystem.
As another commenter said, where's plan 9 when you need it? If you go the FUSE route there are existing 9P implementations for both server and FUSE client you can use.
I've been meaning to build exactly this for a while, and my waiting has been rewarded by someone else doing it!
Had you thought about using FUSE on the server side, rather than patching ffmpeg? Like a reverse sshfs? That avoids patching the ffmpeg binary, which allows usage of wierd and wonderful ffmpeg binaries with other people's patches.
I'd be interested in seeing how well it works with SBC GPUs - many have hardware decoding and encoding, and their vendors love to fork ffmpeg.
I went back to self hosting when Google were going to kill free Gmail for your domain. I have no problems with deliberability. And I have tiny mail volumes.
Pre Gmail I was on Exim. Now I'm on Postfix. I used the 123qwe.com tutorial as a starting point.
The real problems are (1) family members just want Gmail and (2) I have to maintain an email system.
My high school got email access for students in 1997 (New Zealand). We had to pay per megabyte for web browsing. There were services you could email URLs to, that would email you back a text rendering of the page. So I used that.
They had a fairly smart UI for following links. They would appear as footnotes and IIRC you could just hit reply, type the footnote number, and then send.
Yes, you are being too paranoid. Once booted into Openwrt the router will only be running Openwrt code. I guess there's the tiny possibility of a backdoored bootloader but that would have to be a pretty sophisticated backdoor!