As said elsewhere, ladders which are inactive due to players going on vacation are not fun, especially at the top. But not allowing vacation just for #1 is not fair. A compromise would be to change vacation rules as follows, just for ladder games:
“If you are player #n in a ladder, you get +1 day of vacation for every 8 days to a maximum of n. Site supporters get +1 day for every 5 days to a maximum of 2n. If however you want to extend your vacation beyond that limit, you lose one place in the ladder for every extra vacation day.”
In addition, you may use that “extra vacation time” only once a year, otherwise you get kicked out of the ladder.