Well, I have something like that on my PC. Using Hex Editor I made 1.23 from 1.24 and named it Jazz2w.exe. That way I could put it in the same directory as 1.24. Now I can join 1.23 servers, but I can't host them and I can't make 1.23 tilesets. Plus JSZ Lori won't play 1.23. :P Maybe I look strange for 1.23 players and they look strange to me, but that isn't a big problem.