If you are looking for a different French experience, but a French experience nonetheless you might want to try Terre-de-Haut off Guadeloupe. It would be one flight to PTP, cab ride to the ferry terminal, and ferry to the island (you might want to consider SFG vs SXM for better flight options). We've done many day long trips there and enjoyed it immensely, although it is a very laid back island. We were planning to spend some time there after Irma altered our SXM plans, but then Maria came along to change our revised plans. Still. we did manage a wonderful day there in April of last year. Air service to the States is kind of sketchy though, so you might be better off returning via SXM/SFG. But, Anguilla is also nice and much easier to get to.