So here is what I'm dealing with. The rotor is very outboard (as pictured) before adding a wheel spacer behind the rotor.
I bought a 5mm wheel spacer and obviously it won't work with just the spacer as the rotor will interfere with the pad bracket (the red line).

The plan now is to add the 5mm wheel spacer and also 5mm washers (the green lines) and use longer bolts.
The lower green line is the outside of the adapter bracket that connects the pad bracket to the steering knuckle. Hopefully the adapter bracket won't then interfere with the caliper body!

Is it safe to shim this here and run longer bolts? I think it's similar to what you were suggesting, Salomon.