You know, those are all good questions. Personally, I don't know that it is worth the risk, if there is one, and I don't know a good way to assess that. I was inclined to get the power beyond kit. The dealer told me before he did the setup that he was going to check with the Deere reps to make sure there wasn't any reason not to do it. I didn't get any kind of a specific response from him on that, so I'll ask him the questions you have posed and make sure that he did follow-up with the dealer.
I haven't used the backhoe much yet, but I would not want to do any damage for the sake of that couple hundred buck. On the other hand, if there's no danger of damage, I certainly don't mind saving the couple hundred. I do think that the PowerBeyond kit would make that 3rd SCV available for other applications, such as perhaps a grapple or something else on the bucket.
I'll let you know what response I get . . . probably on the owning and operating board.
-- Grant