Changing clothes in a hammock: Easy. After you spend a few nights in a hammock (Hennessey for me) you'll learn that even though you'll bounce and wiggle around with your movements, it won't dump you out.
Changing clothes is a matter of...changing clothes. It's really no different than changing your clothes under a low tarp
on the ground, only with a category 7 earthquake going on at the same time. Which you learn to ignore. Really, changing clothes can be done easily in the hammock, or outside under the rainfly, which is a "tarp".