Oh I didn't know you liked StormBramble too! It's funny that you love Stormfur being shipped with both Tigerstar sons.
I can see StormHawk being tragic in canon because I can interpret Hawkfrost kicking Stormfur and Brook out of RiverClan as romantic jealousy, but I can't quite see a similar angst angle for StormBramble because Stormfur is so tied to being with Brook and also having had feelings for Squirrelflight, even if Brambleclaw is defending him staying in ThunderClan. So how would you make StormBramble endgame/angsty/have weight in a canon-compliant AU, is what I mean?
Well to be clear, I'd probably want StormBramble and StormHawk to happen in separate AUs lol (so Stormfur wouldn't be shipped with both of Tigerstar's sons at the same time.)
As for your question: my understanding of "canon compliant" is that it means a headcanon or idea that's not explicitly contradictory to canon. So I feel like by that definition, any version of StormBramble endgame already cannot be canon compliant, since Stormfur and Brambleclaw don't actually get together in the books. (Although you could make the case for something like the headcanon of Stormfur having a crush on Brambleclaw in Moonrise as being "canon compliant.")
Anyway, though, I can still try to think about an AU that at least sticks as closely as possible to canon. So I'd probably have the divergence happen around Dawn. Stormfur can still have his crush on Squirrelpaw and Brook (and Brambleclaw, like I mentioned in the previous ask response on BrambleStorm lol) in Moonrise. But once Dawn starts after Feathertail's death, Stormfur would no longer be interested in Brook romantically. He'd probably be grieving too much to think much about romance at all, at this point. But Brambleclaw would be a big comfort to him at the time (as his friend), and they could grow even closer as the Great Journey happens. Stormfur would start to feel distant from his RiverClan Clanmates, but again though, Stormfur would not choose to stay with the Tribe in this version. Instead, Brambleclaw could bring up that he's sure that Firestar's offer for Stormfur to join ThunderClan still stands, and Stormfur would accept, joining ThunderClan when they reach the lake.
Brambleclaw and Stormfur could then eventually begin a romantic relationship maybe towards the end of Starlight or in Twilight. (I imagine with Squirrelflight being the catalyst that finally pushes them together lol, after getting fed up of the two of them always circling each other. Like: "Ugh! It's so obvious that you two like each other! Just go talk about it already!!!!") You could sprinkle in some angst surrounding Brambleclaw still training with Tigerstar in his Dark Forest dreams, while feeling really guilty because his mate was a cat who Tigerstar attempted to execute when he was only an apprentice.
