This is the libertarian in me speaking here:
Copyright or no copyright, if you want to avoid "a massive unnecessary duplication of work", then make the creator an offer. Presumably, you both stand to benefit from it.
Yes, you could make the creator an offer, or commission another person or people to transcribe or reverse engineer the work, or you could transcribe or reverse engineer it yourself. This would make complete sense if there was no copyright, or if the work wasn't under copyright, IMHO. But isn't copyright essentially supposed to be an alternative to commissioning work? If the government used tax payers' money to commission a work, but didn't ask for the computer file or source code, but rather only asked for a printed book, or a compiled programme, wouldn't this be selling the tax payers short? If there was a significant amount of money involved, wouldn't we expect a protest? Wouldn't people find it offensive? Copyright pays for works with the public's liberty, rather than from the public purse, but does this make it any less offensive to sell us short? I don't think there is a conflict here with libertarianism at all, besides the inherent conflict between copyright and libertarianism, which, if anything, is lessened if we get a better deal for our loss of liberty.
Of course, the point of copyright (and patents for that matter) was to make the amount due significantly more than what someone would offer just to avoid duplication of work.
I'm guessing you're responding to this bit: "Further, that work [transcribing/reverse engineering] would benefit many, but may bring little reward to the person performing it, hence giving little incentive to do it, which is precisely the problem that copyright was supposed to solve in the first place."
To clarify this, I didn't mean to say that copyright was originally intended to compensate copyright holders to the value of the work that would be required to transcribe/reverse engineer their work, rather I meant that copyright is intended to provide an incentive for individuals to perform work that benefits many, and that the work of transcribing/reverse engineering a work is precisely this kind of work--work performed by individuals that benefits many. Thus, while copyright solves one problem, it (nowadays) creates another of the same kind.
What i do like about your concept (even though it sounds horribly like the patent system) is that it has the potential to make creators think about whether they really want to copyright their work in the first place. If a large minority of creators choose not to, and people get to see more of what less copyright looks like in practice and how to build a business model on it, well that opens the door for real change the following generation.
It would be particularly interesting to see what happened if this law was implemented in a small country like New Zealand. I can't see, though why you think it's unpleasantly like patent law because of requiring disclosure for the grant of a right. Surely patent law could only be worse if it didn't require disclosure. Even if you're entirely opposed to patent law, surely you can't think that requiring disclosure makes patent law worse?