Don, the only link I missed to Trillium instruments is one to a 5-course octave mandolin. (I've got to get that site into the instrument links, if someone already hasn't done so.) There are sound samples at the mainTrillium page, and I'm guessing there are other samples around. I've heard people pick tunes on these instruments, but they're quite lovely when used to accompany a song with chords.
I'm not sure about this because I'm not a guitar player, but I don't think the string tension is much higher (if higher at all) than a guitar. A friend once suggested (I have a problem with one finger) using only one string on each course and possibly using nylon strings.
On adaptability of instruments, I believe you could drop the standard tuning and tune in an open chord. I've seen folks play guitars on their laps like dulcimers, or fret with the hand on top of the strings instead of around the neck. (of course these last two involve re-learning chords)
You sound like you're looking for a guitar with a smaller neck than normal and low string tension. I know there are 4-string guitars ("courting" guitars?) out there.
I know you said you're looking for a fretted instrument, but I thought I'd throw in hammered dulcimers. You don't need to do anything but hang onto the hammers, they sound beautiful (although maybe not the sound your friend is looking for) and they aren't difficult to learn how to play. (Yes, to play well, but to just get a good sound to accompany songs - easy.)