This is probably a good feature, but this post isn't about it. I would imagine an offline version of the prototype that a client can access at xd.adobe.com. With all the comments, specs, details etc. but in some sort of PDF or maybe HTML but offline. Clients like to have something locked in a safe or printed out in a folder. Needless to say that transferring anything in the Adobe ecosystem to a client who has zero interest in having an Adobe account is a useless idea.
Thanks for sharing your idea. I would recommend posting this idea on our XD UserVoice page for keeping a track of it. Please do share the link with us here as well.
Thanks,
Harshika