Don't forget Hierarchy Opacity is more complex than it seems. It's not just about syncing stuff.
I'm pretty sure we all want Construct to consider a whole Hierarchy as a "single image" when it comes to opacity.
If I have 3 objects stacked on top of each other and part of the same Hierarchy. If the Hierarchy is set to 20% opacity, I don't want to see each of those Objects through each other (like if each Object had a 20% opacity individually).
We probably want the whole hierarchy to be at 20% opacity, not individual parts.
Also what if one of the child had 50% opacity and then its parent changes its own opacity from 100% to 10% opacity ?
However if one day Construct had this possibility to render a Hierarchy as a single merged stuff, it would be nice.
Maybe it would also allow us to have effects applying to the whole Hierarchy as if it was a "single image/object".
But then it raises other issue regarding ZOrdering with other Objects that are not part of the Hierarchy. => most probably this "render as single image Hierarchy" option should be an option we don't want in other cases. And the ZOrder/Layer of the whole Hierarchy would be the ZOrder/Layer of the parent. (Child original ZOrder/Layer wouldn't be useful anymore, except for defining the ZOrder for each Objects that is part of the Hierarchy and maybe the position if Layers have different Parallax/Zoom scale)
=> it looks a bit like a rabbit hole
A probably easier way to achieve all those things would be to add the possibility to instanciate and reorder Layer at runtimes