Regarding the account creation fees, I think this fee should be in HBD, and not in Hive

I agree with this. It likely wasn't originally because SBD didn't 'activate' until after the first post payouts (3-4 months after chain launch). And then SBD/HBD didn't work very well. So there was never motivation to do it. It also doesn't seem like it is ever going to be a high priority change for development, but I won't say it can't happen.