Suggested

offline rule

is it possible add a "offline rule" that avoid entering in the race?

of course this rule can be activated obly by the host

People have asked for this sort of thing, quite a few times now.  The standard reply is usually that those at Igp towers would prefer if all managers were online for races, although it is not frowned upon to set up an offline league.  This just means that you will have to find other ways of determining player's offline status.  Watching from another account would be easiest.