If anything deserved a separate category in Special Purpose Vessels first, it would probably be "Pollution Control Vessels." Of the 15 photos I've added to that general category, 11 fall under that umbrella.
I still don't see why a yacht supplier is any different from a crew vessel not used for oilfield purposes. Or a clear line between what defines an "Off Shore Crew Boat" from one lumped in with the workboat category, as their is no listed definition on the site for either. Clarifying that line could easily provide a suitable home for yacht suppliers in an area where people are bound to look for than anyways, and in line with their usual classification in Equasis.