Berry
I agree that is an option as you point put.
However I think the whole "Sorry Madam/Sir the bank is not available to you"
card, do you really think we should go down this route?
And if you fly the freighter you know that the roster keeps changing quite a bit, so "your" preflight crew study has a 50:50 chance of being correct at most.
On top of that although the bunk is at the captains discretion but I'd like to see the captain who is going to refuse the bunk a fellow aviator, knowing that he/she has just operated through their night.
Keep in mind that it is an individuals's choice to have their CoS changed.