There is a big issue with this. Many of us own a lot of champs, but may not regularly play a certain role. If we get forced into said role, we MIGHT not have a champ at mastery 2 that fits the role because lets face it, how many of us have the time to grind out all the champs we have already learned, again, to a high enough rating that we can say to an abritrary system that couldn't pull old data that doesn't even exist anymore to say "Ok, you can't play this champion. You might have over 50 games with this champ, but I don't have any recordings of it, so screw you until you have proof you can show me that you have grinded out the points to play this champ."
I own 120something champions, to just play the 3-6 games with each to unlock them in ranked play AGAIN would be anywhere from 350-700 games. Just because I haven't played a champ since mastery came out does not mean I do not understand how to play them. It could easily take upwards of 600 games to reliably have my entire champ pool reunlocked. And if you had just unlocked a champ, nothing means you know how to play them to just have mastery 2. That can literally be ONE game if you get a ridiculously good score because you played against people who happened to duo with sub-30s/low bronze while you are plat+ and play like it. You would at least want it to be M3 to be used in Ranked, which is even MORE games for those of us who just happen to own a ****ton of champs.
I don't play ADC regularly. I hate the role and only play it to keep my proficiency at it decent, with rare exceptions. To just have a champion pool large enough to play the role reliably, I have to play 20 games according to you playing a role I don't want to play, just to ensure I don't have any BS come up.
This is fine for new players. Old timers though this is just a horrendously stupid restriction.