Every time I pick my wife's knife (my #2 knife that I put a generic ho wood handle on), I remind myself how light and nimble the knife feels. Granted, the knife is thin, but the lightness of the handle is partially responsible for the weight.
This got me thinking about using some of my koa unstabilized on smaller knives like my 180mm gyuto. I am also in a process of making handles from layered birch bark, This one also should be pretty light. I will treat both with some sort of finish, but both will require minimal maintenance with some natural oil/wax mixture (I will come up with something).
I have made a handle in unstabilized koa before, and it fared well in a home environment, besides, I am thinking about capping the ends of koa with blackwood (maybe even make slented D, with a blackwood endcap).