This patch is based on an old work of Koani and working like a charm (months of tests on my friends server). I updated again for mangos and I think to shared here...
Patch for Mangos Relase Date: Sat Nov 12 21:24:50 2011 +0100, [11846] Changes to default target selection.
Assign a new leader when current leader is logged-out (time for leader relogin is configurable).
Also fixes:
* Some instance resets, when leader crash client, etc... (no removes member on logout)
* Member out of range is logged group cant summon it. (because group member status is now updated)
Write by me and based on Koani previous work
http://pastebin.com/EnrZnsyp
Cu and thanks for review my code