If I had to have a slash WSD ship myself, though, it'd probably be Campion and Vervain, also of the show. I like an enemies to lovers dynamic. Feel free to give me funny looks.
Now there is a ship that would have to develop over a long time, as turning them from enemies to lovers wouldn't be easy. Maybe it would have to start even before Woundwort took over Efrafa and established his system. I think it would have to require Vervain to become a little braver and less "I'm here to chew grass and find traitors to Efrafa, and I'm all out of grass".
That'd be a grand idea, actually. Even before Woundwort, they find each other impossible and hard to understand, and they butt heads and kinda challenge each other as such. Vervain is a enormous coward, but he's perceptive and clever, most of the time anyway. Campion is brave and strong and pretty smart too, but he's more Black Rabbit than Elahrairah here. Both of them want Efrafa to improve, and they probably have to work together, but they operate in different ways. I can see them really complementing each other's personality and methods in their younger years. They cover each other's bases, Campion pushing Vervain to be brave and keep his chin up, and Vervain coming up with tricks to get them both out of trouble.
Then once Woundwort arrives on the scene, Vervain gets more cowardly as he clings to Woundwort and Campion gets more uncertain of the entire ordeal, and you know how that goes. I'd have loved to seen Vervain and Campion reunite post-Campion's death. I don't quite remember the timeline, haven't the show in a while, but imagine that, Campion finds Vervain instead of the Down rabbits, and he drags Vervain out of his own mess, the way he used to when they were young. Vervain asks Campion what happened to him, and Campion asks "Whatever happened to us? And the warren?" and they talk. If nothing else, it's an interesting angle for character development, especially on development starved Vervain. I admit my biases on this one.
Stop giving me ideas. This sounds interesting and full of potential and I've already got fanfics to write.