I can support this. Only way I see it being added would be as you said, needing to have the specific runes for the spell you are using. If added, defiantly would like to see this through-out all spells. This can be a pretty decent source of magic xp for ironmen for sure.
Despite not necessarily being needed as we have the teleport wizard and other methods of getting magic experience, I would also not mind seeing this get added. Support.
for example gives a reason to craft laws which are more xp than nats and would switch up the training process, as a 10hp im limited and have to be creative with how I go about training.