I only suggested the Skua as it is a boat one could build inland and trail to the sea. The Gypsy would be a much more comfortable boat to live aboard.
Saturn does have a small nacelle already. It also has much less room in the hulls, and especially in the cuddy, than Gypsy. You can see the difference by looking at the sail plan sketches. Saturn is designed as a fast cruiser, so has less freeboard, less room but a bigger rig than Gypsy.
All the Wharrams I sailed (sails which included a trans-atlantic on Wharram's own Tehini and thousands of miles on the prototype Pahi 35) pitched badly when sailing to windward when compared to my transom sterned designs. It is an unavoidable problem with all canoe stern boats, however many hulls they have.
Windsong will be quicker to build than Skua, but quite a lot slower to sail. Personally having built, sailed and lived on a Windsong (Cockleshell Hero) and a Gypsy I'd go for the cuddy boat every time.
I hope this helps you and others chose the right boat.