Your question is probably better suited in an economic theory forum where this open ended question is discussed at length amongst scholars. You are making the Keynesian argument that the ability to adjust the money supply is inherently good for the economy. This is contradicted by other scholars, mainly from the Austrian School of Economics. 

The very reason bitcoin was created was to have an immutable and predictable money supply in response to the dissatisfaction with an array of factors associated with traditional currencies with elastic, inflationary supply founded on Keynesian principles. 

With any argument you give that inflation in such and such economic scenarios may be good, I am afraid you're preaching to the wrong choir, as it is implicit that bitcoin holders are adherents of the Austrian School that ultimately believe on the whole that fine tuning an elastic money supply is not a good thing and feel very strongly about not inflating the money supply. There is no indication that the bitcoin community would ever deviate from that consensus. Nevertheless, no one is stopping you or anyone from making a fork of bitcoin to test if there is a market interested in an inflationary bitcoin.   

As I mentioned, whether adjusting the money supply is good or bad for the economy is an open ended academic question, with no consensus amongst scholars of economic theory. Bitcoin is the first real world experiment of a deflationary currency where this idea can be tested. Bitcoin does not stop other inflationary currencies from existing and time will tell which currency people choose in various hypothetical economic scenarios.