I like the idea of everyone having to have a licence. The cost of having one for children or seniors could be either negligible or zero; we're not talking about a revenue issue here.
The real question is how do you get ALL fisherpersons, young, old(er) and in-between, to be aware of the regulations and "bought-in", i.e., clear understanding that the regs apply to them, period, not to mention starting to develop some sort of a conservation awareness/ethos.
I like the thought of having to pass a short test in order to get your licence. The licence candidate would at least have had to read the regulations in order to pass the test. Could be available on-line. I'm not talking about a university entrance exam here; just a short test to require someone to basically prove that they have at least read the regulations and have a basic understanding.
And maybe for anyone under 16, a parent/guardian has to pass the test too, in addition to the <16 person, in order for the <16 person to get a licence (even if free for them).