Koa is quite attractive, as illustrated by the following photo of a 1928 Weissenborn "Style 1" constructed entirely from that species. Note that the guitar is almost FULLY hollow, the sound compartment extending from body, through the neck up to the headstock.
This guitar is highly regarded by slide/bottleneck musicians (e.g. David Lindley) despite its simplicity. (I've "heard" that Style 1 copies are now made in Spain.) Apparently the sonic qualities of this wood species were known and appreciated some years before the application to flat-top guitars.
Oddly, the qualities were then forgotten until recently, LOL. Nice to see so much interest - probably a direct result of the Taylor influence.