The notion of planning a cruise around mooring availability is rather limiting.
Cuttyhunk has a decent anchorage outside then inner harbor, which I have anchored in arriving from all "directions" and all hours of the day and conditions. It is one of the two locations where I have dragged in 20 years of anchoring (once), but all the rest of the times the hook stayed. It has eel grass. The approach is very easy in most conditions where you have some visibility.
I seem to recall years ago there was a boat which came by to service the anchorage and selling seafood and picking up trash... but maybe I am dreaming??? Does Aldo still sell his baked goods in Great Salt Pond from a skiff?
It is a convenient stop over if you are transiting the area on your way to the CCCanal, MV or Nantucket or heading the other way to Newport, Block or points west.
The anchorage is exposed to the north, but the prevailing winds are SW and some SE when lows come through.
Anchor out and enjoy the peace and quiet.
Another nice stop to stop is Tarpaulin Cove on Vinyard Sound side of Naushon Island midway down Sound. It's protected from the northern quadrants and exposed to the southeast, but it is completely undeveloped and has good holding.
There's not a hell of a lot to do on CuttyHunk but a short walk, some snacks and maybe buy trinkets and momentos.
Use your hook, save some cash enjoy the freedom and flexibility it offers.