Wow, thats some nice stuff!
For a German weapon collector, there are two I'll NEVER own. Jesus, they are expensive.
I would buy one of the Japanese copies, they are super nice, but hard to find too. Sarco had some but those scumbags won't ship dummy guns or copies to NYS, which makes no sense since they are not illegal here....
But, your friend has two exquisite pieces there. For the love of god, he really needs to shoot them, even if it is just once! George Peterson (big time Fallschirmjager collector) fires his....if you have ever seen the book "Death From Above", the Collectors Grade book on the FG-42, that is him on the front cover, and several of the guns in the book are his....and there are pics of him firing them in it.
And, hell, even if god forbid the worse happens, and a part breaks....I don't think that would even effect the value that much, they are that rare....