Maybe it would be less confusing for the pilot if the switch to ILS mode could only happen AFTER the last waypoint in the route unless manually triggered by the pilot actively selecting a runway and a join?

That seems to be a good suggestion. SD follows the enetered route and only allows itself being kicked into ILS mode after the final waypoint. This would solve all potential problems the pilot might have with a premature switch while not taking away anything of the convenience.

-- Chris.