There are a lot of reasons why someone might want to queue for a specific lane, be it practicing a bottom lane strategy together with another player, practicing ganking for a friend in a particular lane as a jungler, or trying out a core team composition with two or more friends across multiple lanes. As a practical example, let's take a look at what might go through an average player's head, and why being able to queue for a specific lane for practice would be a desirable option for them:
You've been playing a lot of ranked lately, and have a win rate of 85% in all positions except for jungle, which is your weakest role with a win rate of only 35%. Wishing to improve your performance in this role, you queue for a normal game to practice your jungle play in an unranked environment.
Scenario 1: Upon joining the game, another player calls the jungle position before you and automatically locks their champion with Smite selected. This denies your practice time as that role.
Scenario 2: Upon joining the game, you select your champion with Smite selected before anyone else, but another player calls the jungle role in chat, proceeding to also select Smite as a summoner spell for their champion. You get into an argument in the chat, and eventually the other player threatens to ruin the game (AFK/Feed/Troll) if they do not get to play jungle. Because of this, your choices are either to practice jungle in a substandard game environment, or give up the role entirely. In both cases, This denies your practice time as that role.
Scenario 3: You call the role of jungle in the chat before anyone else and select your champion with Smite selected before anyone else as well, and proceed to lock in your rightful selection. You then realize the other four players on your team have all queued together, and one of them selects and locks the jungle role despite not having called it. The group of friends threatens to report you and/or troll you by not helping you in the game if you don't switch roles or dodge the queue. This denies your practice time as that role.
How would a system to queue specific lanes be implemented?
Method 1: The interface for the game would remain the same as it is currently, being very simplistic, and by default, having a check-box marked "I'll Play Any Role" or "I Don't Want To Queue For A Specific Lane" would be selected, meaning the new feature would not interrupt the current system. Underneath the first check-box, a second option labelled "I'd Like to Queue for a Specific Lane or Role" would be available, and upon clicking it, a final choice of one of the five standard positions would be selected by the player.
Method 2: A completely separate tab from the current "Blind Pick" and "Draft Pick" options could be created labelled "Practice Role". This would preserve the current chat-based role calling system as well as allowing the alternative method to be created as an option for players. Players who play in this new game type would first be required to select which role they'd like to queue for.
I don't think the game needs this, players should be able to work out team roles for themselves in chat. It's true that players should, and often do, work things out in the pre-game champion selection chat. However, just because an agreement of roles is reached doesn't always mean all the players are completely satisfied with the role they received. Adding this option would allow players to be sure they got their desired role, and create a better overall experience for everyone.
This is a wall of text and I didn't actually read what you wrote but this is an unnecessary feature because I just call top and I get it no problem! You are one of many reasons why I believe this system would be a great addition to League of Legends.
Won't the queue times for really popular lanes like Top and Mid take forever? I would certainly expect that if this system were to be put into place, that the queue times for said popular roles would, indeed, be higher than the others. Despite this, I think by having it as an option, if a player really and truly wants to practice that one given role that the extra wait will actually be a lot more time efficient than if they were forced to play an entire game as a different role. Besides, we're all used to waiting on that one guy running League on the wooden toaster powered by gerbils, and I'm sure players would find ways to occupy themselves during the wait in one way or another. If the wait is really that bothersome to them, the option to not queue for a specific lane and use the current queue times would still be an option.
That concludes my wall of text describing a rather simple suggestion. Maybe give it a thumbs up if it's something you think is worth considering, or don't, just wanted to get it out there since it's been on my mind for quite some time now. Take it easy.