My K1100LT panniers got banged up so I proceeded to repair them and repaint with MITA bedliner.  I like the way it turned out but with hindsight I would like to share a few things I would do differently.
First the repairs.  Since these bags are ABS I used ABS glue to repair on the inside of the pannier and to build up a damaged corner on the outside.  Then a fine line of superglue on exterior cracks.  Followed by sanding to provide a tooth for the bedliner paint.
I removed the latches but I should have just masked them off.  Lot of extra work reattaching the latches, ended up using 10-32 screws and tapping the latches.  Masking tape is available at auto paint suppliers in narrow widths that go around curves nicer.  Bought a bonding spray and bedliner spray cans at the auto paint supplier also.
I was apprehensive since I have never painted before but the bags were so patched up I thought I could do no harm.  Bedliner is a 2K 2 part spray can.  I learned to keep a distance and move the can fast as it will lay down a heavy splatter coat if you do not.  Several light coats later and I have some good looking panniers.
Hope this helps someone who has some crapping looking panniers.

I've done a couple of set of cases in LineX truck bed liner.

In addition to taping off where the latches mount it's a good idea to also tape off the rails on the bottom where the hinge pieces mount as well as the roundels and reflectors.

For the Gen III bags I also remove the rubber scuff pads and tape off those areas too. Those are a PITA to remove without tearing them but it's possible if you're careful and take your time. I used roofing tar from a grease gun tube to reattach them.

I use blue painter's tape to tape things off.

Locks can be reattached with rivets:
https://www.kbikeparts.com/otherstuff/lostkey/K.Side.Case.Locks.Rivets.pdf