Suggestion: Firefox OTG
There should be an OTG mode for Firefox. It's sort of like a guest account on public PCs. Basically, a "PPC" mode in Firefox should be turned on to note that the browser is not for personal use, only in public PCs like at libraries and internet cafés.
You can sign in using your Firefox account, and a 2FA request will be sent to your mobile devices running the Firefox mobile app. You can call this feature "Firefox passport"
This will allow sync until you close the browser window.
Also, when visiting others with a PC with Firefox, you can temporarily enable this by clicking "Sign in as a guest" in the hamburger menu (Is that what you call the 3 lines in the right of the awesome bar?)
Again, temporary sync until the browser is closed.
The people who answer questions here, for the most part, are other Firefox users volunteering their time (like me), not Mozilla employees or Firefox developers.
If you want to leave feedback for Firefox developers, you can go to the Firefox Help menu and select Submit Feedback... or use this link. Your feedback gets collected by a team of people who read it and gather data about the most common issues.