Replay Button for Last 30 Seconds

I know Riot hasn't added a full game replay option because it would overload the servers pretty fast. But instead of a full game replay option, why not have something to save the last 30 seconds of gameplay to your computer, maybe for a teamfight or a baron steal you want to show your friends. I don't know what the implications of this would be, but I would definitely appreciate having the option to save small parts of games.