Basically what you are wanting would be to have a match run on a previous patch, or to be able to piece together parts of previous patches in order to create a different version of the game, which would essentially be it's own, unique patch.
The problem that I see with this would be that it would be unlikely for there to be any consistent volume of players who want to use a specific patch, and each patch would need to be run out of a dedicated server.
The only way that I can see Riot making something like this possible would be to have previous patch iterations available for download and an option to manually override the client to run from a different patch source. Players could communicate on the boards, or other sites in order to host servers from which specific patches will be run.
It would be interesting, but it wouldn't be run or sanctioned by Riot, so you would also very likely run into hackers, cheaters, and trolls who are much worse than they are in the game currently.