{SPUF} -> [Petition] [Suggestion] [Steam Pipe] Previous TF2 versions/builds are available for the players

[This is the petition and the suggestion discussion thread. Please, post a comment, not only a 'signed']
The idea is about making possible to download any past update and play on the same version of server(s). Since the Steam Pipe (when it is up) merges both TF2 and TF2 Beta being the same client, I see this option could be implemented too (if no technical difficulties*, such as "VALVe delete all the updates after the newer update is created").

This option could be available via Settings of the game (eg., click with the Right Mouse Button on the game in Library > "Choose the update > [List of updates]). Of course, the default update is the current one. If you want to play the newest version of TF2, you need to exit the game and choose (in some kind of Settings) the 'Current Build'.

For example, you download the patch from the February, 2009, which was a Scout update. No further updates and patches are available for your game (maps and weapons/cosmetic items too**). Bugs, glitches, etc. are there too, for your enjoyment. So, you downloaded the update and search for the server that has the same downloaded patch and play on it.
(If you know how the S.T.A.L.K.E.R. update system (sorry, no update news on Steam) works, you understand me clearly.)
Or the update when the game has been released. Or the patch that adds Polycount items. Or the Engineer update. Or the update when the crouch-jumping have been broken. Or the update that broke the gamemode modifications' (made by community) models customization. Or any other update you want to play on.

P.S. I am all for the productive/constructive criticism.

*It would be very-very great to have a VALVe staff comment here.
**The only thing that must not be updated is the backpack. Let me explain this note: All items that were added later are in your backpack, but they become not available for using (reminisce about how items aren't usable when you try to use any tool on them - they become grey), if they were not existing on that update. The item drop still works, adding any existing item to your backpack (but, as I said earlier, you won't be free to use them). Plus, there must be no glitches, related to items (such as painting the Cowmangler 5000 or the Pencil Pusher). No buying retired (or deleted) items, etc. No gaining promo items, etc.

Link to the thread on SPUF.