More or less related to bug 41147 (T43147). Iceweasel team may consider Mozilla's ESR version in their forking work. However that bug was turned into talk about Firefox forks, so I start a new bug here.
Firefox is said to have an "Extended Support Release"[1] which is recommended to be used "by enterprises, public institutions, universities and other organizations that centrally manage their Firefox deployments"[2] by Mozilla. We may want to support that version too (just an older Firefox with security bugs fixed AFAIS).
[1] http://en.wikipedia.org/wiki/History_of_Firefox#Extended_Support_Release
[2] http://blog.mozilla.org/blog/2012/01/10/delivering-a-mozilla-firefox-extended-support-release/