Welcome to RIBnet!
I presume you've looked at the used Redbay examples? As a diver myself, I often wonder about their utility for diving. With a stern ladder, you could certainly work four divers and a dry cox'n.
Crusader and
Benbane are both on the market.
If you're in the market for new, they did a stunning 9.1m for
Aquaholics with a stern lift. No cabin but a good example of what a custom rib build can be.