I loved it! What a difference it would make if Lex had been female, and yet you made it all work!
There was one line that I especially loved. I'm not sure if you meant it to be funny or not, but I had to chuckle. (Please forgive me, I've forgotten the appropriate method of posting quotes, so I may screw this up.)
"She’d done the fake moustache thing before, but it had been easier recently to let Clark take the male roles."
I love how you have Lois "letting" Clark take the male roles, because for her that's not necessarily a given. She's an "I can do everything" kind of woman, and also can be very emasculating to Clark at times. A lesser man may not be able to handle working with her.
Anyway, great story!
Rose