Here's a question. If casting had been different and Dylan had played Scott while TPosey played Stiles, would you still ship Sterek, or Derek and Scott?
Oh wow… ok, that is kind of an evil and amazing question, actually.
~This answer will probably come across as not being particularly Scott/P*sey friendly (though I don’t think it’ll be in any way harsh or hateful either), so just a heads up about that.~
So, alright. The thing about acting, and character development in TV shows vs say novels, is that character is a collaborative effort and so much of who a character is comes from the actor, acting choices, and so much of relationships comes from actor chemistry. So much of what we as fans have latched onto and fallen in love with about Sterek (and about Stiles in general) comes from elements that weren’t scripted –– lingering looks, subtle touches, hints of emotion and nonverbal reactions. Even with every line and every plot point the same, a Stiles played by P*sey would be an entirely different creature, establishing an entirely different dynamic with Derek. (And one that, I’ll be diplomatic in saying this, I believe would be far more straightforward, to script dialogue, with fewer layers.) While there’s plenty written into the characters, and plenty of lines and scripted moments, that lend to how well suited Stiles and Derek are for each other, none of that would add up to anything if the chemistry and unscripted character choices weren’t there.
So I can probably say with pretty good assurance that if P*sey were playing Stiles, I’d be unlikely to ship Sterek.
As for whether I would be shipping Sc*rek instead… it is hard to picture a world where I shipped that. Let’s just start off with that being clear. However, we would have Hobrien’s chemistry going for us, as well as Dylan’s subtlety and nonverbal acting choices, and –– as I said –– that is a huge part of character development, and would change the character of Scott, for better or worse, immeasurably. A Dylan-helmed Stiles handled Derek in season one with a mixture of fear, defiance, raging attraction, and the occasional spark of grudging respect. So picture those elements layered into Scott’s character, with him being afraid of what he was becoming and how it would affect his life (rather than generally annoyed about how it interfered with his dating and lacrosse). Even without changing dialogue, changing plot, the core chemistry between Dylan and Hoechlin would affect the entire development of that season.
Season two –– and the “Master Plan” finale, in particular –– is much more of a hard sell. Could the damning you may be an Alpha, but you’re not mine retort be salvaged with a softer tone or an apologetic look? Would Dylan have thought to reach out and catch Derek’s hand afterward, help him to his feet? Would there be some way to pull a relationship back from forcing a paralyzed Derek to bite his enemy?
The other thing to consider is whether Dylan playing Scott might have changed the actual script. I know I’ve been going on the premise so far that everything would be the same except the actors, but I do believe there’s a precedent for Dylan changing the intended script slightly. In “Echo House” (correct me if I’m wrong) the writers/Davis wanted there to be an actual sex scene between certain characters, and Dylan said he was uncomfortable with that so they agreed to fade to black? If that’s true, it’s possible that a Scott!Dylan would have looked at “Master Plan” and thought –– hey, um… this doesn’t exactly feel like a heroic move right here. This kind of makes my character seem like a huge dick.
And while I doubt the writers would go back and actually edit much of the finale arc because of actor concerns, I can definitely see them being persuaded to squeeze in a few seconds for an (incredibly necessary) apology.
If this was the case, and if Dylan and Hoechlin continued to make the kinds of acting choices with each other that they did in canon, I guess it could be possible that I’d ship Sc*rek instead. But this would be a very different Sc*rek, and a very different show, than the one we have now.