I think the hue and cry from the user base is pretty clear, and that the *technical*, not just aesthetic, issues with the forum are both formidable and undesirable from a productive business standpoint.
I "vote" to return to the old VB forum on a temporary basis. I encourage management to then bring in a subject-matter expert on forums and SQL data migration. I firmly believe that with coding expertise, an expert could migrate the VB data to any other platform, including newer versions of VB.
I understand the desire to keep development in-house. I might be wrong that you have not obtained an external expert. However, that's not clear from the outside. Hiring qualified help has got to be cheaper than how it's been done so far.
Ken has said they have invested more than 800 hoursover time in attempting to upgrade the forum. I'd hate to see that turn into 1600 hours, but that's where it seems to be headed.