"A comment from MaHuJa" -- just now recently? We did talk about it back then, remember?
First thing, I would migrate my ffg guide to something I assume is a bit more stable than my own host.
A single login for all the services is a good idea; I hope you get it working.
I'll add to it when I find quirks (the type the thread you likely saw the referred-to comment in was about); I'll try to help "formatting" - presuming we're thinking of reasonably the same, at least; I can try help admining it.
But I'm a bit on and off so if you needed one person to "patrol" it every day I wouldn't be the one. And I can spend weeks on the "off".
I assume/hope you'll be using mediawiki?