Good grief. This chap has been asking for advice since 11th October!
Surely he needs a big (8m plus), twin outboard engined, beefy-boat.
Just imagine all those big fireman clambering all over it in their drysuits and double/triple tanks.
Such as :
Zodiac, Humber, Willard, ASIS, or Gemini to mention just a few.
This would also give you the advantage of special build so it will to YOUR spec.
Go ask the military what they use-might be a touch expensive but you probably don't need bullet-proof tubes (for example).
"Ribbing-the most expensive way of travelling third class"