It is not particularly common, but it does happen. Resign your Navy commission, and speak to a Guard Recruiter about enlistment. You'll come in at grade E5, and will need to complete WTC and AIT for your MOS. You'll retire at the highest grade honorably held.
I was a Naval Officer and enlisted in MN ARNG. I am still fighting the BIG ARMY for my retirement as an officer 03E. I had enough time when I redeployed from Iraq that I went into the Sanctuary Program and retired 01MAR12. How does USC 1206 Apply?