For your purpose, a camera carrier, the FMA Co-pilot will do what you want.
It will keep the wings level, and a constant fuselage angle at a particular power setting.
You do the "heading hold" mode the wing-leveler provides for aerial photos.
Here's a photo I took this morning with a side-looking camera. Note the "same road"..
The plane deviated sufficiently in heading between two photos that the perspective changed enough to make the images not fully "stitchable".
For a vertical image this isn't all that important, but when looking obliquely perspective does matter..