Even this we had issues with - we wrapped the entire build environment and script in a dockerfile, but depending on system configuration you may or may not have to run docker with sudo - it just so happened that reviewer's environment required it, while ours didn't, and the reviewer needed specific instructions on what to do in this case.
Another time, they failed the review because the reviewer's VM _ran out of disk space_ (which we only learned after digging into the issue, as the first report just mentioned "build errors"; according to later inquiries the VM had ~9GB available) and we had to add some extra build logic to delete intermediate files, just for them. The build is quite large because it involves rust->wasm compilation, but I'd still expect the reviewer's machine to have a bit more space...
Everything described here sounds like your team, your extension, and your software development process are the problem. Demanding >9GB of disk space to build a browser extension is capital F, capital I Fucking Insane. Go yell at the Rust folks about their shitty toolchain and your engineering lead for buying into it instead of blaming people who have enough problems as it is just coming into contact with the quagmire you described.
Simeon from the Firefox Add-ons team here. Sorry about the rocky experience. I realize this is a bit late for your situation, but earlier this year the source code submission docs were updated with information about the default reviewer build environment[1].
It's not a huge improvement, but it sounds like one thing we could do to improve the communications process around build errors is to include a link to this documentation in the notification email sent to developers. I'll create a ticket for this now.
[1]: https://extensionworkshop.com/documentation/publish/source-c...