Good idea.
My suggestion though is perhaps it could be narrowed down to a more specific type or types(ex. Based on Panzer IV chassis, Russian SPG, etc.) By limiting the subject into a specific type or types the discussion regarding references, kit problems, AM and PE, questions will be somewhat focussed. This gives the opportunity for questions of each members to be addressed properly. If for example there are 50 types that could be entered and the flow of discussions (as well as the available resources and references) are concentrated to a few of those types only, some members will be left out. And if those members are also newbies...it could be difficult for them to keep up on their own.
A good example of this is the Sherman and Panther GB. Since the subject is almost limited, the GB starter/ moderator was able to address properly and eqally all concerns of the members.
There has been a lot of (forgive for being blunt) recent GB's lately that were started covering a wide range of subjects...so wide that the GB starters/moderators are finding it hard to keep up with the members' concerns leaving some members doing the kit almost on their own (meaning the availablity of information from the GB was very scarce or none at all for particular subjects).
Since the primary purpose of GB's is basically to assist modelers to build by pooling the available resources (references, tips, etc.) and making them accessible to the members by way of the GB thread, then I think we need to address this issue when starting the GB.
But hey these are just my thoughts...