I have also considered a suppressor for HD and if I had one I would use it. I don't want to lose my hearing. I don't see much advantage to a full auto. Maybe an SBS. Of course my primary HD gun is a 12 ga, so I would have to spend a lot to suppress it.
I guess if I had it and thought it offered an advantage I would use it. If it looked like I was headed to a nasty civil suit that would leave me with nothing I guess I could liquidate my assets, give it to charity, become a hobo before they filed the complaint.
The most likely full auto i would use would be a 9mm AR. I don't own one, but I guess it would be a pretty good HD weapon. It would be worth over 15K I believe. The police would confiscate it when they arrived and it might be a long time before I got it back no matter what.