My editor work with this system:

But Polyvector have several limitations:
If i want to make Zoom a specific zone, with Polyvector it's impossible:

Another problem with polyvector:
when i move the Player on X, in reality I move the stages (and all objects) on the -X axis, so if an enemy is coming towards me, with the speed X: -4 (correct speed) and background locked it's work well, but, when the background is moving (X: -2), I have to compensate the speed of the enemy (or seems to move very fast)!
it's frustrating to move the stages with all object, items, enemy etc....
is the Camera that follow the player ...