One can switch from nusach Ashkenaz to nusach Sfard. I did so myself, under the direction of our rav here on our yishuv. (There are no nusach Ashkenaz shules here.) I did not switch my pronunciation, as he told me that most people who switch end up saying the words incorrectly.
Avhaben, why would you ask your question here? Don’t you have a Rav to ask?