Carol is in her mid-late 30s when she gets the whammy from the psyche-magnetron. It's a good age because it gives her the authority (of a Colonel) while still being young enough to look like a hawt Playboy model).
For the MCU's POV they need someone who will look hawt for a decade at least. So pick an actress in her late 20s and she should still be looking good enough in the role in 2029. This is why Jessica Biel, Chastain, Charlise Theron, etc. aren't my main choices - they're all going to be looking way too old by then.
Emily Blunt would have been best choice but it appears she's not too keen on capeshit nowadays. Hence why I started suggesting Aly back when the casting threads were going a few years ago: seeing as she is easily the hottest blonde of that generation of screen bimbos.