Now ... just for the sake of argument. Let's consider the possibility that I take a look at helping out on one (or maybe two) PCE fan translations that people would love to see get finished.
I don't have any desire to see Tobias just turn everyone else's hard work into pretty, but expensive, "collectors" sets.
Is there anything that can seriously be done to avoid that?
Not directly related but maybe helpful to the discussion:
Within free culture, that is to say the community of people who distribute their work under a free culture license (GPL for software, CC-BY-SA for media, etc, to simplify a bit), the question of commercial exploitation is even more problematic because there is unlike with fan translations, no grey zone at all. You use a license that provide unilateral permissions to anyone to do whatever they want with your work, as long as they follow the terms of the license. It means that the question of how to avoid being ripped off comes up fairly often. For instance if I release a music under CC-BY-SA and make it a free or paying download, whoever has it can resell it and not give me anything, as long as what is being sold still under the CC-BY-SA. Shit will happen and shit happens fairly often with such licensing. Recently Flickr started to sell printed version of the photos made by the users of the service: those who had chosen for a normal copyright protection when uploading would receive a fee (traditional commercial licensing of their intellectual property) but those who had chosen a free culture license like the CC-BY-SA when they uploaded their photo would not receive anything at all. Long story short, even though Flickr did not do anything illegal, it felt like a massive abuse given the pool of free culture licensed photos they have collected for years and could use to make an extra profit, a couple of days later, they stopped doing that because they felt public pressure.
However, similar situations happen all the time with such licensing, and with little consequences as it is done in a much smaller scale. Indeed, the last thing that Yahoo wants is to be perceived as some evil corporations ripping off the work of their users, but that's not the case when the abuse is done by smaller groups or commercial entities. So generally the ethos of free culture is to accept that no matter what you do and no matter how you protect yourself, you will get ripped off by someone, at some point. It is not a question if it can happen, but more when it will happen, and the reason why free culture licensing is chosen, so that for all the others with no unethical intentions, nothing will get in the way of both accessing, using and modifying the shared work.
Of course, this does not solve the problem of tracking ethics across the pool of all the people that might do something with your work. This is why an interesting experiment was done by Nina Paley, who when she released her free culture licensed animation "Sita sings the blues", and seeing the growing success of it, knew that even though she would get a lot of screenings in indie cinemas and art houses, she would not get anything at all in return, and as everyone knows here, donations/patron systems are rarely helping unless you are already a celebrity. So she decided to develop a program in which places who would give her a bit of money for showing her work would be allowed to use some sort of certification, or sponsoring label, like gold, silver and bronze. ON her website she would list only the screening where sponsoring existed, and via her project, the audience would be able to know, in a more transparent way if the ticket they would buy or had bought were only cashed by the venue or if some bit were sent in the direction of the animator.
All that to say, even if fan translations are in a grey area of intellectual property, there is some common struggle to be found here I think. Maybe a similar experiment could be done here.