Not to get political about cosplay here, but the body proportions of, say, comic book characters, are often not realistic on even a purely anatomical level, and it is not at all, at all you understand, a bad thing to be unable to meet those physical traits.
In fact, let’s state the opposite and the obvious, you can—regardless of size or gender or anything else—play any character you want in a convention, and you should if it makes you happy.
If you like Deadpool, be Deadpool. Make costumes of the characters that inspire you, that resonate with you on some level, or buy ones online that make you happy, and go be that character for a few hours, a few days.
Tailor them to what you want to be, mix and match characters, make special props and come up with your own original characters. Please do not let media “gatekeepers” get you down. Life is too short to worry about stuff like that.
Cosplay your way.
Cosplay to bring yourself joy, have fun, and celebrate characters you love and love to hate.
Anyone can cosplay. Anyone who wants to should cosplay.
It’s as simple as that. Follow the rules of cons, be respectful toward others, and be the hero you are inside today.