I understand why you would say that but I don't see that as a big of a problem as you would say.
The way I can see it happen is if all your ranked 4/5's get picked/banned, you'd get kicked out of the queue and it will be treated as if you dodged. This is to discourage people from even attempting ranked until they have a healthy amount of masteries. Which really addresses the second point in my original post.
Another option is to make it like ARAM, where the summoner with the less masteries get priority pick. I don't like this method obviously, but it is an option.
Granted, this won't be a problem if Rito just introduces a ranked TB or blind. Which I didn't mention cause I wanted to save it for another topic but I guess I should've. And ranked TB I believe is coming anyway.
If worse comes to worst, make Rank 5 equal to 2 Rank 4's, or make Rank 3 the new Rank 4.
There's lots of workarounds.
I see people won't like this because it sets the bar for playing ranked even higher than it was, but in the long run, it should make for healthier games.