The best tropes for this pairing are the ones that let both characters evolve beyond their canon roles. I'm always drawn to fics where Toshinori is forced to confront his own crumbling legacy head-on, not just as a symbol but as a deeply flawed man. Seeing Deku inherit One For All is one thing, but watching him also inherit the crushing weight of All Might's mistakes and unresolved trauma? That's where the real development lies.
Time travel's been done a lot, but I love the versions where a post-war, broken Deku lands in the past and has to rebuild a relationship with a pre-injury, arrogant All Might. The dynamic flips completely—Doshinori has to learn humility from his own future successor, and Deku has to unlearn his hero worship to see the man as a partner. It dismantles the pedestal on both sides.
A less common trope I adore is 'mentor loses his quirk first.' Instead of the injury being a distant memory, what if it happens during Deku's tenure as a student? Watching All Might navigate sudden, total vulnerability while trying to guide a protege who still needs him, and Deku stepping up not just as a hero but as a caretaker, forces monstrous growth. The power imbalance evaporates, and they have to find a new footing.
Sometimes the simplest premise works best: just put them in a room for a long, difficult conversation after Kamino. No powers, no villains, just the emotional fallout of shattered ideals and the slow, painful process of building something real from the debris.