> Investments inherently contain risk which would dissuade potential investors if they have a stable source of growth.
Stable sources of growth have existed for decades but somehow most investors aren't just going all in on those. That's because investors care more about good risk-adjusted returns than lame guaranteed returns.
>Investments would have to have very high upside to be worth a stable but lower rate of deflation.
Investments with risk-adjusted nominal returns above 0% are worth it if the currency is deflationary: even if the investment only has a nominal 1%/year return and the currency deflates at 2%/year, that's a 3%/year real return. So it's still better than just holding the currency, even though the nominal return is lower than the deflation rate.
> Secondly, I'm not sure how you can be certain that investment returns, without regard for risks, could be higher than the deflation rate.
Returns on most investments aren't certain in an inflationary environment either, so I'm not sure what's your point.