You know what I think would be an interesting idea for Midoriya Hisashi?
If he was someone who hated Quirks or just his own Quirk. Like just maybe the whole firebreathing has a blow back like how Aoyama Yuuga’s navel laser affects him. And just because Hisashi can breathe fire, even little puffs, doesn’t mean that his body came fully equipped to deal with it. Maybe the whole, Quirks fuck with our bodies hard runs in his family too.
So he hates his Quirk. Considers it a curse. Waited the first moment he could to just snap on a Quirk restraining cuff or something, so that he could live Quirkless or what he calls “free”. Devoted most of his research life to find a way to permanently nullfiy a Quirk, and how to reduce blowbacks of certain damaging Quirks. Fears throughout Inko’s pregnancy and Izuku’s early childhood that Izuku has inherited his Quirk and all it’s shitty drawbacks.
And then one day, Inko tells him that the Doctor declared Izuku Quirkless. that Izuku is declared, not cursed.
Except that’s not how Izuku sees it.
Like can you imagine if the whole father-son relationship is based on this? Izuku at one end of the spectrum: Quirkless and experiences all the bullshit that society gives Quirkless people, and Hisashi on the other end of the spectrum: a Quirk which is great but severely damages him on usage and impairs the quality of his life.