Someone here once called me the "voice of reason"; I'll try to live up to that!
Your market for an adventure trip of 50-80 miles on a small open RIB is going to be limited. If you ask here you will get a very different view from asking the rest of the world. I guess you are looking at 2-2.5 hr trips in reasonable conditions. Most of that will be offshore with little to look at? In good weather that becomes pretty dull for anyone who's not helming/navigating. Obviously in "lively" weather it might be more interesting but you'll narrow the number of people willing to do the trip in those conditions.
Business is easiest with repeat customers, but I'm not sure you'll get too many regulars on a big expensive trip. If it is one of a range of business lines then it might be ok, as the main part of an operation I'd be surprised if the numbers stack up.
I'm aware Americans have a different adventure culture from over here but I do wonder how many people who can afford this trip would also accept the compromises on comfort that inevitably come with baggage restrictions, open boat crossings etc.
Whilst there are plenty of RIB operators in the UK, and even people doing bespoke charters etc there isn't really anyone running the sort of "adventure" trip you describe even in the Western Isles where there is plenty to see, competitive transport is poor. That might in part be due to the cost of fuel, the weather, the range of activities when you arrive, the popularity of "adventure", coding requirements (which would limit a 7m open boat to probably being no more than 20 miles from a safe haven) etc. BUT, I suspect it is because the reality is being driven in a RIB for a few hrs isn't actually a real adventure compared to the myriad of other things competing for your money.