> submitted a Firefox addon for approval a few years back that introduced a separate cache for all the AJAX libs, but it was rejected for silly reasons

I have actually been looking for such an addon. I too clear cookies/cache/etc on exit in addition to using NoScript and a strict Adblock Edge (block social networks/tracking/not just ads). The only area remaining to be fixed would be the AJAX libs to be hosted locally.

Would you consider making a github page or something so you can provide the addon without being in the firefox addon explorer?