I am probably going to write this myself one day, but it's also something I'd just love to read:

Natasha begins dating Daredevil and going on superhero adventures with him, blissfully unaware of Clint's feelings for her. Clint at first hopes the relationship will fizzle out, but when it seems to be heading somewhere serious he has to decide whether to tell Natasha how he feels. I really like the idea of Clint intensely burning for her since before she met DD (i.e. his passion is for her, not due to jealousy/competition).