Greetings all,
I'm a newish user to MOI, so please excuse me if:
1. This 'can be done already' - please let me know how : )
or
2. This has been discussed to death and rejected : )

A suggestion for viewport navigation:
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Please see attached demo video - from another 3D software I use that has this feature.
This is viewport rotation which is automatically centered around the intersection of a 'cursor ray' and first visible object. The small cross indicates that position in the video. This happens automatically on pressing the mouse button for zoom / rotation / pan. It's the most intuitive navigation method I've come across. If the 'cursor ray' does not intersect an object the world origin or screen centre is used (automatically) as a fallback.

I'd be interested to get feedback on this.