Yeah, my host and I were talking about how his Eve Online community gets as many attacks as my old Battle.net community did.It was usually for security reasons. I play Eve Online and was running an 'alliance' forum with over 3000 people. And you'd be surprised how competitive that game really is. Hell, my IPB was hacked into just to gleam 'intel' on fleet movements. Long story. There are a lot of black hat's playing Eve Online and forums are usually a hacking target.
Possible, but desirable?It is possible that by having a vb3 importer only, that could limit the initial number of installations, which would create a more controlled testing environment during beta testing & initial roll out of the product.
I really don't know, but it could be possible.
Those inconsistencies are one my issues with vB4, between that and the errors in the last two updates to forum classic, I've about had it with vB.vB4's schema is very similar to vB3 for most of the important objects like forums, threads, and posts because vB4 is based on vB3. In that sense it shouldn't be too hard to write an importer based on the vB3 importer. However, vB4 on the whole isn't very consistent between major versions. This creates problems for addon developers and may present similar challenges for a vB4 importer.
I have heard about the existence of an unofficial vB4 -> vB3 downgrade script. That might be an option for you.