I have done a few gigs completely unamplified. One that stands out was that we were hired for a wedding reception in a cement courtyard, and for some reason the bass just carried and carried beautifully! I was laughing because we played the whole 3 hour gig that way!
But, here is the rub: No drummer!
I can see how bands in the day, like Bill Evans, could pull this off....they drummers knew how to play very quietly!
However, I am not sure how the high action is really doable.
For example, I could concievably play my bands sets with high action, except that our leader loves to throw bass solos at me.....and I just don't know how I could do the super audience grabbing stuff with high action.
My action is medium. Not so low that it is like an electric fretless bass with all the "mwah" and everything, but definitely not as high as a bass used for rockabilly, for instance.