How are these 144 000 going to assist Christ in governing the people of the earth, from heaven?
Christ said where his brothers are he will be. The 144,000 are pictured as standing with Christ on Mount Zion. He promised them a place in his Fathers house, namely in heaven. This would be permanent (Jesus didnt promise them "a rented temporary room" that they would have to vacate at some later date to move back down to earth). Jesus will forever more remain at his Fathers right hand and co--rulers will be forever where Christ is.
I' m you are not going so far as to suggest Christ cannot govern from heaven
or that God cannot give the 144,000 the ability to assist him to rule over the earth from heaven