I understand what you mean by Two capturing One as a child, but in TP2, this already happens, and it still works, because the branch being moved remains visibly selected, and thus differentiable from any new children.
Anyway, a long as folded branches remain folded during these Up and Down moves, then it will be possible to use TP3 the way that you have it.
Left and Right, however, remain confusing to me. In the following, let each Subhead have subsubheads folded underneath.
If I Select Subsubhead2 and Move Branch left, it also jumps down below Subhead3, whereas i think the more obvious thing should just be to promote in place, creating a new Subhead directly above Subhead2.
The point here being that i should be in charge of the order of items as much as possible. Having things jump up and down when i’m just trying to move right and left can be very confusing and a bit dangerous to the integrity of the outline.
(by the way, i do the above with Move Branch Left. If i instead use Shift-tab, TP3 behaves quite messily. Hard to describe, but if you want i can email you a file)