They won't do an origin again, they will just have Spider-man if he is in any of the MCU productions. And there is no reason why Garfield can't do it, if it's a Spider-man film.
If as Spiderman in the film, they could have a guy in costumer all the time. Spider-man secret identity was secret to nearly everyone but like 3 people until more recently in the comics (movies have done that so badly, everyone so easily finds out).
Hmm, pie.