How are your sea legs Kambo ,
or will it be more sitting on a dock of a bay 8)
The sound devices looks the business alright , designed to operate under all conditions even war zones .
Dont short yourself on a few decent dynamic mics either ,always handy to have , inevitably there will be situations you dont need to risk Neumans due to weather or because its just a party/jam situation.
Its a nice idea to be able to offer an artist anchorage say in a quite bay or harbour or tied up at a quayside ,a total change of suroundings , studios in themselves can be a very intense situation on a personal level , trying to manage the whole show on board a boat will no doubt present its own unique chalenges , theres also signifigant risks to clumsy, accident prone ,or people who've over imbibed even just at the quayside , at sea is another ball game completely , If you are planning on a money making enterprise doing this ,strongly consider insurance implications in a 'SHTF' situation .
Maybe you have years experience on boats I don't know , but if not take any chance you can to learn more specifically about how the boat your planning to use works and sails .With a boat of 70 feet even at a quaside location there will be tons of small jobs that need to be attended too daily ,maintenance just to keep all the systems in check ,
Its boiler suit , a deck scrubber and bucket for you.
A compact mini pa system might be a good edition to the equipment list also , just enough to be able to perform/record on deck with or without an audience or anywhere else the need arises for monitoring or sound reinforcment ,.theres a kind of wheely speaker , rechargeable battery opperated
I'd say being able to offer standalone location recording services without the boat would be a smart thing to do , not just geared towards song writing/pre production , but possibly film tv , voice over ,sports ,even internet broadcasting etc .
There would be all kinds of jobs you could pitch for in your neck of the woods .
best of luck with it ,