I got tired of impatiently waiting for Sparrows to update the original Modesty Panels Removed (https://www.xivmodarchive.com/modid/11835) so I used my newfound modding knowledge to make my own. Mine is a simple model edit; I opened the chiton in Blender and deleted the side panels! Problem solved. Urianger is now delightfully exposed again, as he should be.
Edit: Sparrows has now updated theirs, and I will say that if you're going to use TBSE for Urianger, you're much better off using theirs, not mine. This is because of how vanilla clothing works, and how body mods work. To use TBSE with him, completely, you'd need a version of the chiton refit to a TBSE body, which is not what mine is. I owe Sparrows my life for how vastly improved my Shadowbringers experience was by their mod, and really you should all just go get theirs and not mine.