Originally Posted by metaphysician
Basically, above all else, I don't want to see the MCU destroying the concept of the Badass Normal.
So much this. Of all the characters in Avengers, a big reason why I loved Clint and Natasha the most was because they're normal. No enhancements, no super powers, just amazing agents with these awesome skills. Giving Natasha that agelessness takes away from her awesomeness, IMO. Even if the serum doesn't enhance her abilities at all, it means she's had decades worth of training to do that instead, which really turns me off. I would definitely prefer that whole subplot and her involvement with the Winter Soldier be left out. Having her be a super spy with knowledge of him would be enough.
MCU seems to borrow elements from many different universes, and this is a case that I really hope they don't follow 616.