The Erogenous Tones modules take up a lot of room, but are actually really space effective. RADAR with Blip offers an incredible amount of modulation options, and makes a terrific combination with USTA 
I actually have another autoharp that still has the chord mutes, and still have the ones from this one in a box. I’ve found that it does a pretty good job at resonating the strings in tune and their harmonics pretty well anyway, but have it tuned to a big lovely chord, as the dissonances would ring out some.
I have an exciter stuck to the back close to the bridge:
It works pretty well, though the pickup does pick up some sounds from it. I would like to try mounting a larger bridge with the exciter stuck underneath, I think that would work better. The pickup should pick up less of the exciter that way, as it won’t be stuck to the body as the pickup is. Guess I could try making a bridge for the pickup too, hmm!