Advice on resetting membership each year

Hi guys

After your thoughts on the best way to tackle this, and what impact it would have on existing threads.

I run a social rugby league tipping comp here in Australia with 200 members (maybe more this year).  I've been using the webwiz forum as part of the site and have put some minor mods in the forum then align the tipster login details between the forum and tipping sections of the site (basically, I use common usernames and userid numbers). 

Each year with the tipping comp, I clear out all the previous years players and then setup new ones for the next year when people register so the tipster numbers start again from #1 through to #200.  I was planning to do the same with the forum by removing all members, then adding them back in like I did the first time.   I can automate this with MySQL, so that's not the issue but I'm wondering what impact this would have on existing posts.

Specifically, if I were to remove all the current forum members and create new ones, would the existing posts screw up by replacing the new user's username against those posts?

eg.
Old Year
Member 100 = Fred Smith
Member 101 = John Brown
Member 102 = Billy Bloggs

New Year
Member 100 = Silly Sausage
Member 101 = Fred Smith
Member 102 = Johnny Rotten

If old member John Brown (#101) posted a topic last year and I reset the membership (using the same userid number range as before), would that topic then appear as posted by Fred Smith (who is now member #101 this year)?  

If this happens, then my thoughts are to leave last years membership as is (and make them inactive members) then change my mod slightly to identify what years comp is active.  Once I know this, I could then re-number the tipping userid (eg. this year, start members from #1100 so when I login and go to the tipping, I just deduct 1000 from the userid which will then align with the correct tipping id).

Another idea was to add a 'year' and 'tippingno' column to 'tblAuthor' then send this to the tipping pages.

Any suggestions/thoughts/comments are welcomed.

Not quite understanding you there Bruce.

Are you saying that the original posts/threads will retain the original username, and any future posts after changing the name will have the new username?  If so, that's exactly what I want to happen.

Just in case anyone else is looking at doing the same as me:

This is what I did:
1. Created a new Group in Group Admin with zero access to all functions
2. Renamed all users (except Admin and Guest) with leading or trailing text.  In my case, I added the year afterwards so existing users could re-register with their original username
3. Moved all those users into the new 'no access' group
4. Banned all users in the 'no access' group
5. Disabled PM's for users in the 'no access' group

This basically achieves what I want and that is to retain old posts/threads but allow members to re-register under their old usernames.