You can shoot over the poly and consider it 'undercoat'. There's a guy over at the
www.tdpri.com (user handle rhomco) that has done a few in surf green. Seems to me he has some pic's in the bass forum... looks tasty.
Rhomco's SX-Tele P Bass
He buy's SX P basses and re-shapes the headstock into a Tele shape and has a pretty sharp looking bass when he's done
Probably you should double check with the re-reanch guy and see if there is anything you have to do to the poly coat first.
I've been thinking about doing this as well. I have a Cream colored mid 90's Precision Special (aka Cowpoke) - the poly finish is hard as a rock... I really have no idea how it could be stripped without risking serious body damage so an over the poly might be my answer there as well...