Another option I have been thinking about (which is more work) is to allow people to opt out of the voting game and just earn a straight return on their HP. So we divert a portion of the current reward pool to this new HP staking reward fund or whatever it's called, and people can opt into that if they want, and if they do then they cannot use their stake to vote on content.

I think this amounts to the same thing economically as the proposal, but maybe it appears better on paper, because people don't perceive the inflation loss. I guess one difference is that the method you're suggesting still incentivizes staking versus just holding, if that's an objective. And you can "tweak" things more if you have a variable percentage, rather than just an outright reduction in inflation.