Security isn't everything, there's also accessibility to think about.
HTTPS breaks in many circumstances when it's not needed, including on current browsers.
You can also use a stripping proxy.
Bigger issues I've encountered with actually using Mosaic is that a) it does not support the Host header, so you must have a dedicated IP address, and b) it doesn't like semicolons in then Content-Type header, which most of today's servers include.