I second this. As a long-time vB, phpBB and SMF admin, it would be helpful. Also, it would be nice to have a working importer for (don't laugh) WebBBS, which we ran on several sites for five years before getting something more robust. We have thousands of archived posts we'd like to make public for read-only, but I have as of yet to find any importer that will import those threads. (And I'm not sure if I have the brain cells, or the time, to write my own converter in PHP.) There was a WebBBS to phpBB converter I was able to use for new sites, but it only worked on new forum installations, not an existing one.
On top of it, most importers only treat things as though are converting an existing site. In other words, you can't add a second set of posts/threads/users without eliminating the first forum you've setup. Yep, merge would be really nice for this!
So in essence, we have a running phpBB2 forum I'd convert to xF, and would want to merge in the archived posts from our old WebBBS forum as well.
This is my first post here, but have been active on vB.com and vB.org (which I'll refer to as "the other place"
) for years in connection with running and tweaking a "big board" forum. I am "RedWingFan" over there, alas...