If a situation happens like the one you mention above that would still be against league rules. You cannot get a start from a pitcher in the RP spot. This rule change is more for players like John Smoltz, Joba Chamberlain, etc. I still don't get how this is even justified as a rule. A guy is eligible as a starter or reliever, but you can only use him in the role he's actually participating in. But when a guy is a reliever, but not eligible, you can't use him. It's completely asinine and arbitrary, as well as the opposite of how things were done before.