Exchanging IP to RP?

What are your thoughts on being able to - lets say 25 IP=1 RP - exchange IP to RP. I think it would be great for those people who have every champ, runes etc. and still have left over 100k IP to exchange them. But then there should be a limit for exchanging it, lets say 100 RP a day or so and only if you have every champ and probably a certain ELO(just to balance the system so there are limited people who could do that).

what do you guys think?