Some great points
I am honestly not convinced that there is a will to onboard lots of people. I think the people who make money on Hive don't want to enlarge it because that would mean losing power and share of the reward pool. I would be more than happy to be proved wrong.
More users coming into the Hive ecosystem will drive up the value of Hive. More users also means more interest from developers to build on top of Hive, further driving up the value of Hive.
Having a smaller portion of the reward pool won't matter if that smaller portion is worth more than the larger one was before new users and developers came in.