Due to the difference in number of roomettes in a V I and a V II sleeper account community toilets in the V II, they can't simply swap a V II in for a V I where ever they choose. The booking system can't easily handle an unpredictable roomette inventory. And they would be shooting themselves in the foot if they simply mark every single level sleeper as having only 10 roomettes (or is it 11?) to allow for V IIs here and there.
So, I would expect them to first have enough fully accepted cars and sufficiently trained staff' to completely outfit all the trainsets of one selected route. In my opinion, I think the Cardinal would be an ideal 'guinea pig' as they only need 2 trainsets and 2 spares.