If you have a current reservation that was not made in the home booking period, you could do the above suggestion, and ask member services to re-allocate the OTU points to the reservation you currently have booked, freeing up any current use year points that you could then bank if applicable. Unless there is some sort of rule against this, it should work.
I had to play with points a few times recently, borrowing points from my 2017 use year, cancel that reservation (done online), then called to ask member services to re-allocate to a current reservation in 2016 to free up some 2016 that I could then borrow into 2015 upon a waitlist coming through. It ended up working out for me, just had to explain to the cast member about the re-allocating as she wasn't sure what I was trying to do. I would imagine you can do the same with OTU, as long as you have a current eligible reservation you can allocate to.