I would also vote for putting the X-ref on a separate worksheet and using it as a Trace reference using the Virtual trace.
It makes the best possible use of the Virtual trace tool while giving you the most options in dealing with or working from references including the splitter bars (excellent!!) as mentioned, as well as adjusting transparency between reference and your working plane as well as switching them back and forth. And you can also assign a consistent color to the reference (like red or green) which can make it easier to read and distinguish from your construction element.
But just as useful in your case is that you will also retain the ability to snap nodes, points and elements on your references, so you don't have to guessing. And since the reference is the same as your X-ref, it also remains live as long as you re-load your X-refs meaning that if there's a change in your AutoCAD dwg file and you re-load the X-ref, the Virtual trace will also reflect that change.
Using the Model view options to turn off fills as s2art suggests is also a good suggestion. But the only problem is that as your model becomes more complex and heavier, it becomes difficult to distinguish between the X-ref and the ArchiCAD elements - especially if you're using the same colors and layer system as the X-ref for your model elements.
