Hi OP, I think your summary is good, especially putting a glazed wall in to define the kitchen/living areas. That seems a good compromise between open plan and closing the rooms off if you need/want to. If you can, perhaps sliding doors would be better, to avoid taking up space where they swing open.
Remember what you loved about the house so much when you bought it and try and play on that. Also, think about why you want to move and figure out a way to either improve or disguise that.
One thing that isn't clear to me on the floor plan is that I'm not sure how you get in to Bedroom 4? There's no door on the floor plan and the way it's drawn makes it look like you can only get in to it via your en-suite (unlikely!) or through bedroom 3? It could just be a poorly drawn plan though.
If you were to stay, would you be able to fill in the space under your "flying" bedrooms? Or would that not be permitted due to reducing parking space? A lot of similar houses to me have a garage in that spot which many people have converted to gain the extra reception room.
I LOVE the light fitting in the upstairs hallway though! I wish my ceilings were high enough for that!
The blue in your baby's room is gorgeous too - do you mind me asking what it is?!