Yeah, not a real slick solution to this one and it would definitely take a custom import. Someone would have to be put to the back of the pile. Meaning, either your user #1, or some other early user would need to be given a user number at the very end and then the importer modified for this so it doesn't increment everyone else.
The classic_import.php script would be what needs modified. If it's not something you're paricularly keen of tackling yourself I'm sure there are a few people here that could assist including myself in my off-time.
