The admins of this site have added some basic mods onto the default Lemmy code (like nfsw-by-default), but I don’t think they’d want to develop tags as its own feature.
I agree. The further one strays from the source code, the harder maintenance can be. Just ask Hexbear, who diverged a huge way from Lemmy before spending a large amount of effort making their code compatible enough to federate again.
Clothing is symbolic and can absolutely be sexual. Nudity is often completely non-sexual (just ask nudists). Yet I find unclothing to be much more sexual than someone already being nude.
But even ignoring that, clothes can change the shape of body parts (e.g. push-up bras).