Hi Michael,
good to hear about the import and export compatibility.

I am not sure if this has been mentioned somewhere else in the thread, but for visibilitiy,
it would be good to have three modes (instead of the Visible / Non-visible option):

Force-on (green or yellow)
Neutral (gray)
Force-off. (red)

This is how cinema4d does it, and I find it really good.
Basically, if neutral, then the object inherits the parent's properties (so it is visible if the parent group is visible etc...).
If the object is turned ON, it will alway be visible, regardless of the parent's properties,
if it is turned OFF, it will be invisible.

I find this system quite usefull for organizing large scenes.

Also, how will this interact with the current Hide and Isolate options?
I use these all the time when modelling, so it would be good to have maximum compatibility between this and the upcoming options.
(Maybe the hide options override the Goup attributes, this would maybe be the most logical way of doing it?)