eg. if the search hame is Tom Smith and the spouse is Julie Oaks, the button would change the nae to Julie Oaks and the spouse to Tom Smith.
Okay, but how would that help? You would still have to input / change her vitals so a search could be made for any sources relating to her. Apart from marriage detail, it is doubtful both your Tom and Julie would have other details in common, so why not start from scratch?
I do have some empathy here, as I do get frustrated that I often cannot attach a marriage source for both the individuals at the same time. However, the problem here (usually with England & Wales marriage registration records) lies in how they have been indexed, so whilst I can attach the source at the same time, one of the couple only goes across as a surname.
If you would like to expand on your request - giving an example of exactly how this might be applied and work in practice - i believe that would be a great help.