I’m OK with this as long as we make 16 the age of adulthood. Otherwise it’s a bit hypocritical to say that a 16 year old is mature enough to vote but not mature enough to have a beer.
That is an interesting idea, but hard to implement in practice, to only allow mature enough people to vote. Being mature means different things to different people, but I suspect that even we we agreed on a definition we would find that a lot of adults would not qualify.
You could argue that an adult shouldn't be represented by someone they didn't have the ability to vote for or against. But in that case you would probably need to lower the voting age even more.
If we ever make “K-16l” schooling free I suspect it will come about in tandem with increasing the perceived age of adulthood.
Meanwhile I do believe that 14-18 year olds should be provided far, far more agency than they currently are.