And that's why I started this thread. There's a lot of experience on SB that I've tapped into.
The important thing about "your boat" is to actually get out there on other boats and see what you like and don't like
Sure you have restrictions currently length for you - but if you're going to make an investment, I'd get my license sorted early so you buy just the once. Also slightly longer boats with a wider beam will just make things so more better
I can't comment on your need for a rib, It's my impression they're main reason is that they're light to tow. If you don't need to then why bother (unless there are other reasons)
I've been on small dive boats (max 44') for about 10 years, both club and shop boats. For 4 years I used to maintain teh club boats so have a fair idea about what works in our environment - we as a club made some poor decisions which looked good on paper but didn't perform as expected in service
MY Preferences are as follows
Tanks and gear down the centre, at a height which makes it easy for people to don. with the sides free, back rolls are easy, and the main weight down the centreline gives better roll stability
You'll need basic gear onboard. Large Ice chest for water and perhaps snacks between dives. O2 kit First Aid easily accessible. Life rings and other safety gear
You want the seating arranged to keep the passenger weight toward the stern - too much weight forward and the bow is constantly falling off the plane
I prefer a rear centre helm, others prefer off set. Ladder - placement for ease of entry back onto the boat I despise fin on ladders, others love them. Whatever. but getting guests back on the boat with minimum of fuss is paramount. So make sure it goes deep enough so people can get their feet onthem easily
I would not run a dive boat that only had a single motor. Check how you fresh water flush the engines. If the boat is always in the water some methods can be PITA, so people don't bother and you cause yourself misery down the line
No need for camera buckets nor mask buckets - seriously you're surrounded by water, wash them there
On our sunshade we have cargo nets on the underside so you can stuff small items of clothing - (hoodies and the such like) to keep you warm on the drive back. We have small Karabinas up there too so guests can attach their drybags
Easy stowage for fins when guests come aboard, grab ropes down the sides, stowage for extra weights, spare tanks, Anchor hook for grabbing mooring buoy etc etc etc.
The list of small details goes on. some not being right will be a mear annoyance, others really interfere with the running of the boat. Hence get out on AS MANY dive boats as you can, either as a guest or as a DM so you see both sides. Figure out what works on those boats and what doesn't. Steal all the good ideas - understand why people do certain things certain ways, sometimes there is good reason, others they haven't thought it through, but KISS is paramount.