If by nodes you mean components, what you describe existed just a few versions ago. It was called "clusters". They were temporally removed as they are being rewritten to work more like instances (you create a cluster, copy it, change one of them and both get modified).
Yes, something like that. Although I'm not sure how useful it is to have the components actually seen inside a big rectangle. I guess that's the expanded mode, but you can reduce it to a small component?
I think the new clusters will look as a normal component, you double click it and a new canvas will open with the cluster's definition.
it is actually quite good because when you collapse it you see a square with all input and output channels. those are adjusted depending on all the in and outputs of the nodes inside the group.
this way you save complicated scrolling or switching to different canvases / layers.