I also had a Rohloff shifter on the end of drop handlebars, no problems with cables, but I hardly ever ride out of the saddle with the low gears on the Rohloff.
Issue for me was scraping the side of the rotating part of the shifter when parking the bike against stone walls, etc. This could mostly be avoided by taking more care, except sometimes in ferries, trains, etc. when someone else is likely to move the bike. I moved it to a Thorn accessory bar under the handlebar tops as a precautionary measure to avoid potential damage.
I ran a Shimano 8-speed twist grip hub gear shifter on another bike in the same position for quite a long time, but the Shimano design is slightly different, scraping only scratched the housing for the gear indicator, but didn't interfere with function.
The Shimano derailleur bar end shifters on my old 700C lightweight are quite scratched (been in use since at least the early 1980's), but again, damage is only cosmetic with no loss of function.
A hubbub-type adapter is fairly easy to bodge with a small piece of 22.2 mm straight handlebar, a smaller aluminium tube from a broken camping chair, tent pole, etc. to fit inside drop handlebar/piece of straight handlebar and epoxy adhesive to glue the whole lot together. I expect the small tube could be replaced with a wood dowel.