Not going to happen, and I'm not in favor of this. I'm assuming you're asking for at least level 4 mastery on a champion? Here's the problem.
You now need at least level 4 mastery on 16 champions to be able to play ranked (not a problem for me, I have more than 16 level 5 masteries I believe). Now let's look at this scenario: You're a jungle main, but you queue up for jungle/adc. You get ADC. Can you guess the problem? I'll wait.
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Hello Amumu adc because you DON'T HAVE ANY GOD DAMN LEVEL 4 ADCS!
And if you say make it so you can't queue up for adc without level 4 adcs, it won't work. I'm not quite sure if there are 16 adcs(I'm pretty sure there are though), but you'd then need 16 level 4 adcs and 16 level 4 junglers. And also if you use this argument, there will NEVER...EVER...be another ranked game ever again. You know why? There aren't 16 supports.