I think MCU Tony's reasons for making the Rescue armor would be to protect Pepper, first of all.

*nods*

My first thought was that Tony would be really concerned about Pepper going off and super-heroing but then I realized that the Iron Man suit is SUCH a security for HIM, that it would probably make him IMMENSELY relieved to know that Pepper has one too, and is sometimes (literally) surrounded by the best of Tony.