Omnipotence (having all power) is evidenced through Christ's victory over death when He was resurrected and took up His body again. We definitely believe that God is omnipotent, but we do not believe that a lack of body shows all power, but rather that a physical body is a part of God's perfect and omnipotent character.  
 
If having a physical body is unfavorable or even hindering to God's power then it would not make much sense that the Son of God would choose to be resurrected with a body of flesh and bone. (See Luke 24) It is important to realize though, that God's body is not like ours. His is perfect, immortal, and glorified. 
 
Essential to God's plan for us is that through Jesus Christ we will all receive a resurrection to be more like unto Christ. (Phillipians 3:20-21) 
 
Hope that helps.