As others have advised, nursing is more time consuming than appears at face value. You think that you can work as a nurse and still take pre-med coursework and perform at a high level but quickly find out that after a 12-hour shift of nursing, you have little energy left for anything other than you bed. Your nursing won't suffer but your grades in pre-med will.
Being a nurse won't make you a better physician. Being a good medical student will make you a better physician which doesn't involve nursing at all. The two professions are totally different even though they share the same workspace occasionally.
As a nurse, I agree with these points.
Nursing classes/clinicals require a lot of hours of lab/class time/prep that are not reflected in credit hours alotted.
In addition, despite the "shortage", new graduate nurses are having difficulty in many areas, in getting that first job. Most good first employers want the new grad to work fulltime for a while as well as commit to working for them for several years....our "version" of internship. They would also be reluctant to offer parttime employment and/or new grad internship to someone who is not seen as being as invested in nursing.
The other major (MAJOR!!!!) problem, is for most good nursing programs in any major school/area, openings are quite limited and competitive. There are waiting lists for 6 monthes to several years in many areas. If the program requires more than grades and has an admission committee, you may be required to be interviewed or write an essay. As well as usually your academic record is reviewed by the the admission committee. If there are indications that your primary interest is medicine and not nursing, chances are they would be reluctant to offer you an opening if you are aiming for just doing a couple of years before you get your medical degree.
Much on this BB has been made that an opening in medical school/a good internship "should" go to the best candidate, but also the one that will devote more of their life/time to medicine........ as the openings/internships are a scarce commodity. In this economy, there are a large number of applicants for each nursing school position and these openings are scarce.
For my program, in 1990, there were over 500 applicants for 60 places. The numbers are higher now.