Fragmentation also is a big issue. Not only in the sense that there are separate very different sign languages (American Sign Language has little in common with British Sign Language, they are not mutually comprehensible), but even for each separate sign language you also get different 'dialects' in different areas/major cities, which are mutually comprehensible but have lexical variation depending on the speaker's location/community that needs to be properly represented in your datasets in order to be acknowledged and understood. In some sense it seems the equivalent of what the fragmentation was for spoken languages before the printing press and age of nationalism facilitated language standardization.