Hmm well more of a general concept about what you could do to save the complexities of accomplishing what you outlined...
- Create a (or a series of) general archive forum(s) to import all these posts into... if you did this before your user account work, you could have the poster be anonymous but match up to the original poster's name... right?
Is there any way to sort your user list by post total? If you could do that, you could then import those users with e-mail accounts, who have posted more than x # of messages. If they didn't have an e-mail address, you could take a week or two to post a notice on your current forum, for those users to contact you to attach an address to their account for the conversion.
If you don't have post totals, throw that whole thing out the window.
