That sounds reasonable ... I'll have to find some time to set this up and try it out.
I've also used the ORDER property on the part instances to force single gates of a part onto the same packaged RefDes.
I feel a Mentor "Ideas" coming on ... it seems you should just be able to select the nets, unroutes or pin-pairs, <right-click> and select "Associate Nets" or "Create Associated | Electrical Net" then pop up a box to name it, maybe with a default name so you can change it later in PADS Router (or CES).