Would a requirement to have the end user install a GFCI help? Or, better yet, a GFCI/AFCI.
If I bought an electrical appliance or electronic component, or had one upgraded/modified, and the vendor suggested I buy a GFCI or GFCI/AFCI to protect me from the product, I would probably decide against that purchase. The safety should not be a work around, it should be designed or engineered into the product.
I also provide a written one-year warranty on every amplifier I service, which also protects me from frivolous complaints from the customers. I believe it is a prudent thing to do. This may only be a hobby, but I will be damned if anyone will be able to take anything away from me because a lawyer thinks that I am not operating a legitimate and professional business. This is why I have an LLC, to keep my personal property separate from my business assets. I may never need any of this but I sleep better at night knowing I have it if I need it.