It's hard getting people to give up on their old customs.
The problem you have is not people giving up their old customs. The challenge you have is who gets to set the agenda? I.e. are the decisions of Torath Mosheh Ashkenazim the priority or is the decisions of Torath Mosheh Sephardim the priority? What about communities that are neither Ashkenazi nor Sephardi - like Teimanim, Ethiopians, Benei Menashe, etc.? Do they get an equal say? Often, the decision for someone to give up something is one sided if it does not have a Sanhedrin that everyone accepts as valid.
Further, what is the priority? To go back to something remaniscent of 1st Temple times or 2nd Temple times? Depending on the priority, it may he starting from complete scratch with the basics that had been developed by the most authoratative Sanhedrin we have ever had.
Further, is the goal to have a single nusah for the sake of the Beith HaMikdash that is one thing. If the goal is for all Jews to say the same things across the country privately and communially that is another. Also, is one taking into account the return of tribal land allocation? Along with that comes the potential for differences in tribal and local nusah.
I know personally if a valid Sanhedrin were to be established here in Israel and it was accepted by all Torath Mosheh Jews I would hold by their halakha in a heartbeat w/o concern for what has been the situation for the last 2,000 years. If it is just one person, from one community, setting such an agenda I would hold by it UNLESS that person was a valid Ben-Dawith who was showing
extremely strong potential to be mashiahh, based on MT of course.