This hack is NOT for the faint hearted!
You will definately have problems upgrading to a newer version of vB. The table changes are the least of your worries. Any vB code changes to the newreply or newthread files after this hack has been installed will make it impossible to post due to primary key violations. The changes are minor and it's easy to re-apply to any new release but I wouldn't advise you to implement this hack unless you are confident with mysql and php.
I doubt Jelsoft will offer much sympathy if you ask for support after installing a hack
As far as emptying out the usenet posts to restart... I have a little script I knocked up for that. I'll post it when I get home this evening.