If you set control points, but optimise just d, e and roll
parameters, then the photos will be arranged like prints on a
canvas without any distortion.
You can also reset all photometric/exposure parameters before
stitching. Similarly there is no point using enblend to merge the
photos, so you need to stitch just the intermediate images and merge
them as layers in an image editor.
The images could be merged with borders and drop shadows using
ImageMagick.
--
Bruno