I woke up this morning and was excited that Tim left a comment on my post yesterday. He says:
With this subassembly you can leave the targets as polylines and target the surface for the elevations. If the surface updates so will the corridor.
Similar to your idea using offset alignments and profiles but fewer steps.
Tim, where have you been all of my life? Obviously, I have not been spending enough time with my subassembly trading cards… sorting them, stacking them into piles, committing them to memory and trading with my Civil 3D pals. Those new subassembly rookie cards are so hard to come by.
Since I already had my targets set up in the drawing, I used the subassembly swap trick to minimize the amount of resetting I’d have to do. (Sometimes this works really well, sometimes the codes don’t line up correctly and you still have some work to do. Also try the corridor editing panel for tools like match region properties to preserve targets.)
Once I rebuilt the corridor, I tried doing things like moving the target polyline, and like a parametric dream come true, the tie-in updated perfectly.