If I understood correctly your wish is to totally avoid cam rotation, applying new rotation to the cam or setting new rotation to the cam, etc…
As soon as the cam can be at any location and rotation at moment of applying something to it as per your wish, the options as per my views are:
- Rotate the cam to the object (or center of its side, etc)
- Move the cam so that the object is viewed at its side, for example.
- A combination of the two above to reaching the “perfect” re-location and viewing angle.
As per my guess, option 1 and 3 should NOT be used. Then… you may apply a new location set-up of the cam so that your object is viewed at its side. In general, after such re-location (move) the viewing angle can be any thing between (1-89). By exception = 90. Such a move will be easy - it may be 3D one, but basically you need to calculate the vector between the cam and you object (or a point - center - of your interest) plus a distance vector cause the cam should be at certain distance off the object (center). This kind of move will be absolutelly opposite to panning the object. I.e. moving the cam to the right on X (direction of X coordinate increase) will be equivalent to moving the object to the left on X (direction of X coordinate decrease). The same with other 2 coordinates…
(under certain angle)