Me and some friends would really like to have time to execute moves last until we hit space. But I cannot find a /set option for mods to do this. How do you do it, is it something built into the mod itself?

/set reactiontime [number]

the default time is 15 seconds =].

When you type that, the message will be "none".
Don't worry about that, just reset the game and the reactiontime you set will be there.