This is something that we use all the time in WorkNC, and I believe, would be a welcome new feature in Rhino. In WorkNC, pressing the space bar makes an instant zoom on the current cursor location according to a zoom factor defined in the software settings. If you press ‘C’ it locks this zoom factor. Now I know the space bar is already spoken for in Rhino, but maybe this is something that could be tied to another key. As long as the key is held down, the zoom is in effect. Let go of the key and the previous zoom factor is restored (except, as mentioned above, if you intentionally lock it).
I also find the mouse-over selection much faster than selecting in Rhino, and I have brought that up in the past as an enhancement request for an option to do that. I believe someone mentioned that they were testing that, but there were problems in some scenarios. Not sure if that fell off the radar or not, but I think it is something worth considering.