The problem you have at ISK is that if you wish for leave outside 'crew/block' you have to go through your skipper; then your specialist leader; then OC B and/or A, all of whom can say no and that's before you even fill in a leave app!
Even if you could set alarm lights flashing with 'Refused' leave, what would change? Our lords & masters are not going to turn round to T.B.Liar & co and say 'We can't do that, the guy's are owed leave".
However, I would like to see a 'Leave Buy Back' scheme, because the Treasury would make damn sure that no-one had any leave to buy back.