And if their are idle resource and people then your argument falls apart because idle resource simply decay (both human and machine) and produce ZERO returns, any positive return is better then that. The history of interest rates clearly shows that interest dose not ONLY reflect an average of growth rates or even the average return on investment activity (which is what you meant to say).
If the growth is happening elsewhere, perhaps the capital owner should consider scrapping the equipment and recycling it into a more productive industry. (Note that this is a restatement of my previous post. Recycling equipment is an example of "leaving that capital available to those who can [at least match the global growth rate]".)
Just as an aside, in the situation where capital is idle and literally rotting in place, where is the growth coming from that is causing deflation? You do remember that when the money supply is fixed, deflation comes from the growth of wealth (which includes capital), right? And that growth isn't delivered by angels or storks, but by the application of capital.
In that situation, growth would be low, and thus deflation would be low. People would have an incentive to lend at low rates during those times. I really do wish that you had paid more attention in high school chemistry class so that you could see dynamic equilibrium as a thing of beauty. It must be hell seeing the world through your eyes as the struggle between various external ghosts and spirits.