Support exp buffer?

You know how there used to be no gold items for supports... and how jungling items now grant bonus xp for killing jungle camps... This is because before supports used to be at a huge gold deficit and junglers would often fall behind in level.

But supports do fall behind in level too - they have to go warding and should be roaming often, and all this time they miss out on a lot of xp. I am not sure if there's any reason for supports to be underleveled and punished for doing their job, so I suggest adding an "experience buffer" for supports (item or rune [I think rune's the better option, that way roaming midlaners can also use it]).

For example each time an enemy minion dies near you the buffer generates and stores a small ammount of xp (up to a maximum). When out of lane and out of combat the stored exp is slowly released, until the buffer is empty and needs recharging.