ya. find a set of internal buck horns, cut them off and slug them on a set of dragbars.. (making sure they are not wider than 36" so you can still fit through the front door like D-Day)
as for adjustment.. the easiest is a housing adjuster you see on brit bikes and the like.
you dont "have" to run a solid wire. infact i find they bend sometimes and then you have drag. i made a throtlecable out of a current "spring return throttle cable with twisted wire" i picked up and ran it on my super B til i went to the CV... both resulted in a push pull action anyway...
Their were only two draw backs to the origonal internal cables. (1) the origonal set up had a very long throw, almost a full turn from idle to full open. This has been eliminated by the aftermarket vendors. (2) The throttle stays where it is when you let go. A good thing to rest your arm when riding. But a bad thing if you come off the bike (ie Dump the bike).. I have seen bikes on their side running wide open untill someone can shut it off. That said internal throttles do look cool..