PTO isn't vacation. IVDs come off of your vacation weeks, and only pay 4:15 each. A hypothetical PTO drop would come out of your sick bank, or even a completely new and seperate bank, and pay the value of the trip.

Make it subject to coverage, put blackout dates, fine. I want it for things like, say a friend's mom died and I want to be there for them, or my house needs a repair that I can only schedule when I have a trip, etc. Right now your only options are to drop and not get paid, burn an IVD(s) and mostly not get paid (and lose a day[s] of your vacation), or lie and say you're sick.