I like your idea of logging a speedhacker like this
Code:
L TimeDate Bla <Jon><><STEAM_ID:I:AM:1337> Possible Speedhack !
Another thing, if an admin is there, you could bring up a menu giving them options to things to the possible speed hacker
Code:
WARNING: Detected possible speedhack on CLIENT: Jon
1. Ban
2. Ignore
3. Spectate