1. I think you're underestimating how far Bitcoin prices can fall, during a fiat deflationary period. In that case, Bitcoin prices would completely collapse, if you just kept emitting the same amount over and over. NGU long-term, but not necessarily every month or every year. The volatility would be wild, to the downside.
2. The population will eventually begin to shrink, worldwide, and you'd have more and more money chasing fewer and fewer goods and services.
3. It's sort of the "pre-mine" effect for early adopters, who had to put up with crazy shit for years, so that would be a gigantic rug pull.
4. It reduces the hardness, so that you'd have to spend it faster or lose purchasing power.
5. No real point, as we have Lightning and lots of places after the decimal.