For the fill button make it so i can but fill but not....

In the current ranked system I am just fine with how the things go but most of the time i don't want to force myself to chose two of the three roles that i enjoy playing in solo que that being top mid and jg, yet I am unable to que as fill for just these three due to the fact that when i do I'm always forced on my least favorite role in solo que that being sup (dont get me wrong i can still do stuff as the sup and i did sup main the last season this isn't what the post is about) I do understand that the fill button makes it so then ques can be made faster by forcing people to do roles that most others are not queing for this is a key thing for such roles as sup that are not normally qued up for (yes i do know that you can still carry teams and win games as sup I'm not saying anything about the role other than it is not normally qued for)