Why not give us a mastery to convert extra CDR into AP?

So since my idea in another thread received a positive response, I thought I'd make a thread about it.

A common complaint amongst a lot of support players is that, while they like the stat, there's too much CDR on support items. While items are meant to have a trade off if you build them for one stat they give even though you don't like another (See something like how Rumble might like RoA for the health but since it has mana he doesn't build it) CDR is a bit different since it's one of the only stats in the game that has a hard cap on it and even in the case of other stats that have a cap, they require rather ridiculous itemization choices to hit.

So how could we make people feel better about wanting an item that has CDR even when they go over the cap? My idea is to create a mastery to convert CDR into a useful stat.

http://i.imgur.com/HTqVLtL.jpg (A general idea for what the image could look like) Resourceful For every 1% of CDR you get over 40% CDR, you gain .25/.50/.75/1/1.25 Ability Power

This mastery would be a tier 3 Resolve mastery. The reason for this is because there's already a lot of utility masteries to compete for use in the Cunning tree so putting it in the Resolve tree helps give supports something to pick in the Resolve tree without having to give up a mastery in the Cunning tree.

You may notice that the AP gained from it is not equal to the gold value of the CDR it comes from. 10% CDR is worth about 26 gold while 10 AP is worth about 10 gold. This is on purpose because this is supposed to appeal to supports and tanks that can often go over the CDR cap if they build a lot of supportive items by letting not feel as bad about doing it and by making it still not give you full gold value it will discourage mages from taking it so they can buy nothing but without wasting any stats.

Obviously numbers can be tweaked or even its position in the masteries but I'd like to know what other people think about having something like this.

Ah, one more thing, I deliberately made it so that it gives AP for CDR over 40% so champions that like the Intelligence mastery (Which are mostly supports) can get even more bang for their buck from this one.