Well, it is not very uncommon that people change majors in America, it should not create any issues. If you have an admission from a school for MS, your DSO can advise you on the COS process and it should go smooth without any issues. It is very hard to predict that at this point as the RFE is dependent on the job and your complete profile at that time, it is upto the discretion of USCIS. Also, you need to be aware of the fact that for you to work on H1B, you need to still go through the lottery…Planning for higher educaiton is a big decision and you need to consider everything before you proceed. Personally, I believe that education has to be driven by passion and not just a way to get around and find some job. You already have a Masters, maybe you can find ways on how to use your MBA to get a job…If you do NOT like MBA jobs that a different story…Going for Higher education is more than paying money and getting a STEM degree, it is your time commitment…