3D Viewport pivot mode

A while back I was trying to build a workflow for painting 360 panoramas, this is hard to do using a pen and tablet in blender since the mmb can only be set to orbit or pan in a 3D View.

The idea would be to allow someone to navigate with the viewport by pivoting, similar to the the way one would in Google Street View. Meaning dragging with the mmb pressed would pivot the viewport, and scrolling or ctrl + mmb would change the focal length of the viewport.

This would have to be something you toggle since pivoting would only be useful in certain scenarios such as modeling in tight spaces and painting interior spaces. I presume the toggle would go next to the existing Navigation Gizmos.

Besides adding an extra gizmo to the navigation gizmos I got really close to achieving something like this with a python addon but I had to control a camera because I couldn't control the viewport focal length with python and the view3d.rotate operator couldn't be overloaded because it's core functionality that wasn't written in python or something. Meaning I had to constantly be in a modal operator to have full control of what the inputs do at any given time which interfered with other operations such as the toggle button I put in the toolbar.

Perhaps creating an easy way to temporarily replace navigation operators with custom one's, and adding more control over the viewport orientation and focal length via python would be a tidy solution, as not only would that allow me to achieve the controls I need in an addon but it would allow a lot of flexibility for custom viewport controls, for instance, when I am using a pen and tablet in grease pencil or sometimes when I am texture painting on flat objects I often want the orbit and pan controls swapped as drawing on a tablet usually puts me in 2D art brain where 3D rotation doesn't exist and I expect the mmb to pan not orbit even though its the opposite of what I expect when I'm using a mouse.

Or maybe theres not that many things that a viewport actually needs to do and the things I mentioned just need to be introduced into the core functionality and I can submit the input dependent orbit and pan swap as its own idea.