This is something that we've looked at recently.  While it's not in immediate development, we've put provisions in place to allow for creating POs from service orders somewhere down the line.  It's significantly more complicated than what we have for creating POs from sales orders as there is the possibility of the SOs being continually added to during the lifespan of the SO, whereas sales orders are generally static.

Terry thanks. I would actually prefer when creating a PO that you could designate the SO it is to go on. That saves double entry and ensures it is charged.

If / when this functionality is added, it will be from SO to PO only as the sales orders are now.  If you need it to go the other direction, it would have to be done in a custom version of where you can specify the rules of how to handle all of the variables that would be involved in going the other direction.