How to communicate with the advisor if someone wants to downgrade his PhD to Master in university A and then apply for PhD in university B? I am a M.Sc. graduated from a developing country and I recently got admitted for PhD in one of the reputed universities in Canada (rank 20-30th world-wide), say university A. In fact, because of the compulsory military service I could not exit the country with an M.Sc. admission letter, so I ended up applying for the PhD programs.
In general, I am completely happy to do my PhD in A and the university is considered a good place to research, however I thought that by doing research with great scientists there and completing a M.Sc. degree I probably would have a better chance of getting a PhD admission from a better university (e.g. a top-10 place), say university B.
As I have an interest to work as faculty in future, studying in B may slightly  increase my chance for my future carrier. 
So, I would like to know is it anything bad or immoral to express my idea to my potential advisor when I arrived in Canada? Please note that I would be perfectly happy to work as a PhD student under his supervision in case that he is unwilling of the downgrade but I fear that the proposal in itself burns the bridges or implies that I have not interested in doing research with him. All in all, I would like to know that what is the best (safest) way to express my desire to my advisor?

P.S: regarding the university policy, I checked and the university accept it if the advisor agrees.
Your wording here is perfectly fine for explaining your situation in university A. Your advisor is the one who works there and knows about internal dynamics of the university.

And also, name of the institution is important at a certain level. What values you as a scientist is the quality of your publications and thesis. Finishing a PhD in university B might be a challenge, but you can set your goal to make better publications than people who have PhD degree from B.

For the last point, there is always postdoc, which will probably be the most productive period of your life. You could finish your postdoc at university B and achieve your goals anyways.