l asked this question to my JW friend, and here is his reply:
JW's don't believe that the 144,000 are called because Christ requires "help" or "need" to reign over earth. Jesus was a master worker with Jehovah, however it was not because Jehovah was incapable of creating and thus required Jesus help.
No where do our publications state that the the heavenly calling is due to Christ's incapability as a ruler.
The 144,000 are called due to God's mercy, undeserved kindness and it was God's purpose that obedient human beings from earth who are declared righteous be given the opportunity to share in the Kingdom Rule.
2 Tim 1:9 :
He saved us and called us with a holy calling, not because of our works, but because of his own purpose and undeserved kindness. This was given to us in connection with Christ Jesus before times long ago.
1 Peter 1:3:
Blessed be the God and Father of our Lord Jesus Christ, for according to his great mercy he gave us a new birth to a living hope through the resurrection of Jesus Christ from the dead,