I'm voting for this because I want no Battle Helpers for brawls and tournaments.
I am okay with Battle Helper being used in modern ranked at this time to allow its use as a tool for learning.
However, I know some Leaderboard players are concerned. Perhaps the ToS could state that use of Battle Helper makes one ineligible for Leaderboard Prizes? Then simply requiring a user to make a checkbox in their user settings "I do not use any third party Battle Helpers" in order to be eligible for Leaderboard prizes?
Some degree of honour or trust would be involved. But hopefully the biggest Battle Helper services would perform an API check and they would opt to not provide BH functions if a player makes a claim that they don't use it.
The reason for including modern ranked is as you said is the competition aspect of this - via your leaderboard comments. That is where people OBVIOUSLY compete. But there are many many more places where people compete for rewards too. The goal is to make the human vs human modes "competitive" and not just be "bought" by the use of tools that create better teams through automation.
I'm actually trying to stop an arms race before it gets going. For instance yesterday, one of the Legendary Dragons proclaimed that their "bot service" has now developed a battle helper for use going forward. They did this only because they felt disadvantaged to the players using xbot for instance.
We saw the same thing with bots in general in the past. First we had a guy called j69 that botted at a high level. Then Bubke got tired of him winning so much and developed his bot. Then Archmage and XBOT came along and had to compete with those guys. And in the process, most players turned to botting or they left. Worse, no new players would join as the experience was horrible if trying to play against these machines.
So these 2 proposals are meant to stop an arms race before its gets started. For instance, I have already spoke with the Legendary Dragon Dev @NoKo | Legendarytools.io and he confirmed he would disable his battle helper if it was against the terms of service. His clients just don't want to be disadvantaged if the terms of service are not clear. Put another way, they will follow the rules if the rules exist. But they will not stop the automation if the terms of service still allows battle helpers.