Taking gap year studying math and doing some internships before applying for Msc finance

Hi, I am a 22 year old Norwegian currently in my third and last year of a BSc in finance. I was going to take a master in finance at my own school (probably ranked 2nd in Norway), but during the summer i have considered to take my masters abroad instead. I have looked at many schools now, and i am very interested in the Msc finance at MIT, MFA at LBS and Msc finance at Imperial college.

My profile is:
GPA: 4.13 of 5.0 (Expecting to boost this to 4.5 after this semester, and 4.7 after my last semester).
Internships: None, but have worked part-time for over a year in a big international pharma company, and currently as a teaching assistant at my school.
GMAT: Not taken yet.
Abroad studies: None, but went to summer school for two weeks in Shanghai this summer.

Since my GPA will at best be 4.5 when I am going to apply in february/march, and I probably won't be able to spend much time on the GMAT, I am considering to wait a year before applying.

If i do this, my plan is to take a year study at University of Oslo (Year studies are normal in Norway, usually people take them if they are unsure what to study, and tuition in Norway is maybe 100 USD a year.) If i do this i will study mathematics, and take courses in Calculus, Linear algebra, probability, programming and numerical math. I have taken math in my bachelor, but the highest level here is basic linear algebra and differential equations. I will also spend a lot of time on the GMAT, do some volunteer work and maybe take a internship.

Since the scholarship and loan from Norway won't be nearly enough for a Msc in London or US i will have to take private loans also, if i wait a year i will probably have a good shot at some external scholarships which will enable me to take the Msc without taking any loans.

I would really like some inputs on my thoughts.
NB: I know that the best thing would be to work for some years and then take an MBA. Sadly, getting a job in finance with just a bachelor here in Norway is nearly impossible.