This is unlikely because it would undermine the idea of Jillian wearing the pants, but I wonder if the twist will be that she puts the F1 or F2 or F3 (probably just the F1: Ed?) through a final test where she refuses any symbol of commitment (like a ring) from whoever's left. Then maybe Jillian says that they should only plan on moving forward with her if they're willing to slog out the challenges of real life dating after the show especially after they've seen that she's connected strongly with a few other guys.
So then we'd have scenes where the F1 is shown ruminating after his proposal has been rejected and going through a thought process of facing "reality". But the happy ending will be the F1 coming back and making a really strong statement of commitment to Jillian sans engagement and saying that he's thought about what they have together and he wants to pursue it in the real world. That way the audience gets its happy ending and the story that's told is that this is a relationship that could make it in the real world.