I imagine that Winair will be operating like a bus line even more than they usually do - show up at the gate and they will fill up the plane with whoever is there with a ticket.
To be honest, isn't that the way that the SXM-SBH flights have always worked on both SBC and Winair? The departure times are mere suggestions and they will generally put you on the next plane that has some space. That has been my experience but in recent years I have had larger parties of 6-7 so we have chartered with SBC so we didn't have to worry too much.