Well, in talking with the PTC, if I have them install the piezo, they can also install a battery cavity to make that bit easier, which I would likely do. I'm not sure how quickly those piezo systems kill batteries. But, like I said, I think I may be better off just keeping an eye on the used market.
Having PTC do the job and installing a battery cavity sounds like the way to go. I'm assuming they could do this to a used guitar or did they say it would only be done on a new guitar?
Did they indicate how much it would run? If so, send me a PM with that info, I don't think they want pricing discussed publicly on the forum.