Stat Conditional Abilities

I think it would be cool if Riot came out with (or reworked) a champion who has a passive, ability, or their entire kit that does something different if that champion has one statistic relatively stronger than another.

What do I mean?

• When total AD > or = 120% AP
• • Active effect on this ability will buff the champion for + 10% / 20% / 30% / 40% / 50% bonus attack speed for 5 seconds.
• When 120% AP > total AD
• • Active effect on this ability will buff the champion + 10% / 20% / 30% / 40% / 50% total movement speed, decreasing over 2 seconds

This ability would be a great utility for an engage as an ADC, as well as provide safety for a AP Mage. (I understand this is not properly balanced)

Why?

I would really like to see more champions built this way because it would be interesting to see a champion have a noticeably different play style based on how they are built. This is of course just one example. If a whole kit were to be thrown together with these kind of abilities, I think some really interesting things could happen.

Please give me your ideas for what stats and effects you think would work well together.