I think that would be Awesome. I have toyed with the idea of writing a GECK manual myself, but as you know I'm way too deep into my project to back out now and as such I have to limit my non-mod committments. I'm currently working for Cipscis on his validator and have done some mod work for MystykStar, but the GECK manual is just too-big a topic to do in anything less than 100+ pages. If you don't end up writing one, and once my mod is complete, who knows - but we need at least a year of stick-time on the NV-GECK too as it's coming with a bunch of new features that we'll have to figure out. Also if its possible to do an asset-transfer from a Fo3 to a NV mod (swappin gout FormIDs for references in NV), that will take time too.
Either way, one desperately needs to be written one day. The WIKI is Awesome for modders as the reference for stuff, but its not a manual.