You could try doing soem top mounted Colored led low noise fans on some of the Duos,youd have to cut plastic out to give a proper airway and rig a power supply for it.Also soem kind of internal out audio like how jamma arcade boards can do,for self powered stereo sound output.
A long time ago,I took one of the Capcom arcade fighter sticks for Genesis,the white one,and a 3DO control pad board with the earphone audio output,and modded it into the joystick,and drilled a area on each side for 2 small audio speakers,and placed grills over those areas to keep from damaging the speakers.I had it trimmed out real nice and clean,and had made a 3DO logo using a cardboard logo from a game box,lamenated,and supergluded to the center of the joystick.ALl in all it was very nice,and I sold it to a game store owner in Hot Springs,who gave me a nice amount for it,thinking it was official.That was one of the best joystick mod jobs I have ever done.