I've been lucky so far - every time it has changed me to the new layout, I've been able to hit the "switch back to the old layout temporarily" option.

Have you considered using a client like Thunderbird for your email? You can use a web-based account, but access it through a client on your home computer, which you can customize as much as you like. Thunderbird is the mail client analogue to Firefox for a browser (like Outlook and Internet Explorer).