In 1958, Rabbi Israel Brodie, the Chief Rabbi of Great Britian ["Make Britain Great Again!!"] asked Dayan Yitzchak Weiss [who would later move to Yerushalayim and become the head of the Edah Hacharedis] about changing one's accent ot the modern Israeli pronunciation for tfillah.
Dayan Weiss was strongly opposed.
1] One must keep the minhag of his ancestors. This applies to nusach hatfilla as well as one's pronunciation.
2] The traditional Ashkenazi pronunciation distinguishes between a קמץ and a פתח. This is significant because the name of Hashem must be pronounced with a קמץ. In modern Hebrew - there is no קמץ.
3] The intention in changing is not religious and לשם שמים but for nationalistic purposes. Chas Vi-shalom!! [This is interesting because Rabbi Brodie was a passionate Zionist as opposed to Dayan Weiss who was passionately not].
In long hand:
