Lindsay Porteous in Scotland has built dozens of instruments like dulcijos over the years (three courses, diatonic fretting, small soundbox). He has a houseful of them and I don't find any of them very effective.

A much more convincing instrument is the Turkish cumbus-tanbur (cumbus body with a tanbur neck, i.e. much longer than a dulcijo). You play a tanbur on the upper two courses rather than just one - the player's left hand rarely moves far from the middle of the neck. It's quite often bowed ("yayli tanbur") and there are a few YouTube videos of it in action. The fretting is microtonal and it can play the full repertoire of Turkish and Greek art music.