You are not gonna get the perfect match. A lot of what you are asking for is going to be expensive or custom and expensive. For a boat that size you should put it on a trailer. A dolly of sorts will bring it in or out of the water, and could travel 200 yards. Jet Ski (PWC) Dolly 24- from Wheeleez, Inc.
There are other dolly options out there too. Then you have to store the dolly.
An engine large enough to move 6 people plus luggage, should be at least a 40hp and probably a 50hp. That means a crane to get it on or off the boat, or a couple of really strong people, and that is questionable as motors are awkward.
Two of us can move my 4.2m boat around. We can beach recover it over soft sand by removing most of the weight and carrying it separately (Anchor in crate w/rode, electronics tower, and fuel tank). I can launch it by myself since that is downhill. BTW no one makes transom wheels large enough to launch a boat that size over a soft surface. (At least I couldn't find any, so I built my own for a hefty price. Then recently built the front dolly.)
6 people in a SIB is tight or at least with my smaller 4.2m boat. We do it sometimes but we only have day packs with us for hiking not luggage. It is very noticeable in the power needed to plane that much weight.