In this sort of economy, holding money is not “risk free” as you put it. There is a very real opportunity cost. Furthermore, if some group of people prefer to hold cash, instead of lending, then the price (in terms of interest) that the others can command, will be that much greater, assuming the Demand for loanable funds hasn’t changed (and there is no reason to assume that it has).
You suggest that when purchasing power is increasing (because prices are trending mildly downwards) that people will be generally less inclined to bear risk for a nominal return. I say this is not the case, because in that sort of economy, a nominal return (i.e., $1 becomes $1.10 when repaid) compounds the real return (i.e., the purchasing power of $1.10 is now $1.21)
It seems that due to this effect, there would also be more incentive for some people to take the risk, since their return would be that much greater, having been augmented by a real rise in purchasing power/productivity.
[NB, I may have misread the last point you made. Oops.]