But then a savvy inspector would come along and catch the absent drain trap, thus killing the whole deal 
Ahhh true!
Just get one of those flexible doohickies(aisle 9 @ HD), that’ll work! 
With PVC most problems can be solved with a different part or a hacksaw.
Until you can give us a pic. I would use this under the tailpiece.
I think I understand the original poster’s problem as I have an identical problem. And I have a pic. The cabinet is new, the iron drain is probably original to the 80 year old house. The P trap in the pic is just propped up there for illustrative purposes.
I think ckratzer got it right, those are the only two options I could think of. The old cabinet had a slot cut in the floor to accomodate the P trap. I was hoping to avoid that but I’d like to avoid re-doing the drain and vent too. We can’t always get what we want. Thppt.
