My question ... can it be done in Pakistan ?
Why not ? I hope one of the Sunni or Shia Alim will take the initiative and make it happen.
I love the argument about Hajj and Namaz being performed in unison then why not Eid namaaz , the same argument can be stretched a little and can be applied to all the namaaz.
In a majority of Masajids in USA the Muslims of various sects pray daily namaaz together.
Namaz a Eiadain is also prayed jointly by all sects at one central place in many cities in USA.