Without Quentyn, however, wouldn't the queenmaker storyline be incomplete?
I don't think so. I could see something like (terrible fanfic warning):
1. Cold open in Dorne, Sand Snakes and Trystane and Myrcella all in the Water Gardens hanging out, Doran and Hotah watching above, to briefly show them as normal people living their lives before Ellaria shows up with the bad news.
2. Ellaria confronts Doran alone, wants him to call the banners and March north. Doran refuses, no interest in war.
3. Scene of the Sand Snakes talking about their father, Ellaria arrives, they ask what Doran said. When she says Doran plans to do nothing, Obara gets mad and says they should go break in and kills Myrcella themselves as revenge. Ellaria slaps her because that's dumb and Oberyn would never want them to hurt that girl. Trystane is going to marry her and she's going to be family, and they've all grown fond of her while she's been here. One of the other two Snakes throws out the idea that they don't need to kill the girl to start a war, just crown her instead.
4. Ellaria and one or two of the Sand Snakes go find Myrcella in the gardens, where she and Trystane are making out and whining about why his dad won't let them get married yet. Ellaria counters that it's such a shame the rest of the country doesn't follow Dornish law and treat women equal to men in inheritance. Then she would be Queen and no one could stop her from marrying Trystane. And she's such a smart girl, too! Would make a great queen. Basically trying to plant the idea in Myrcella's head to work her over. Then, if they want their fight scene, Jaime and Bronn can arrive for a much less silly version of the fight. They could maybe not talk about the Snakes as fighters at all before that, so that it would be surprising when they stand up to Jaime and Bronn, instead of underwhelming. Hotah comes and arrests everyone, probably just as they're about to kill Jaime, for dramatic effect, and from there they can pick up with whatever they're building to currently in the show. No Quentyn or Arianne needed.