Let user specify that close-up lenses were attached to a lens for accurate correction
Is this worth the effort? There’s quite a variety of add-on diopters, some better than others. And no limit to which lenses they can be attached to. The best ones (achromats) don’t seem to require additional correction IMO. I use a Canon 500D and have no complaints even when using it with lenses it wasn’t intended for like an ultra-wide zoom.
Agree it is not a priority item.
User could enter the diopter corrections, perhaps stacked, (e.g. +1.0, +3.0)
This info could be taken into account generically for geometric correction and vignetting. Chromatic aberration could be accounted for using the adaptive correction feature suggested in another post.