I would love that!
It would be even more useful in two ways:
1. The fixtures do not lose their focus when the focus position is moved. (In addition to: the fixtures do not lose their focus to a focus position when the fixtures are moved)
2. You can freely focus a fixture after assigning it a focus position. The focus then becomes relative to that focus position.
example: 6 fixtures are assigned to focus position DSC, 3 of those are front, 3 are backlights. The ones in the front are focused on the head and small, the ones in the back are whole body. The centre of the beam needs to be higher for the three fixtures from front. Once you have made the correction of the focus, it should stay this way and a move of either the fixtures or the focus position changes the focus relative to their original focus.