Very simple. Being able to watch replays of your LD games. In the score screen after every game, there would be a button labeled "save replay". If you click it, the games copies the temporary file of the match to your hard drive and lets you watch it, in-game, as if you were in spectator mode. With pause and rewind included.
Presumably, I'm assuming this is possible because spectator mode is possible. The server is giving your client all that information, so wouldn't it be possible for the client to then store that information and play it back later? If I'm not mistaken this is how replays in SCII work.
yes good idea. Although if this was ever considered, it wouldn't be a stand alone patch, but part of a larger Coliseum or UI Redux, which i doubt will happen anytime soon.