I think German Wikisource has a rather high quality standard compared to a lot of other Wikisource projects. There are several projects which don't do proofread at all or request scans. That is where we should start to unify the Wikisources.
German Wikisource is also one of the project which have the longest time experience with PR. In all this time we never had problems with IPs proofreading. The community is small and it's usually the same few people. Our contributions by IPs are overviewable (check Latest Changes for it) and AFAIK we never had miss-use by IPs. That's why I have problems to understand why a plugin gets developed in a way that is more secure but less user-friendly when there never were problems with security but some with user-friendlyness (e.g. currently you should not be colour-blind if you want to change the status after proofreading because there is no description of the radio-buttons; I don't consider having to create a special monobook as user-friendly, especially considering that not everybody is able to do that just like that).
Next thing: if somebody wants to cheat he will cheat. Switching of IPs does not bring anything since there is sockpuppeting. It actually causes the opposite. While we can see the IP-adresses and can check if they are from the same range, we can't do the same with accounts. Only checkuser can do that and German data privacy law is rather rigorous when it comes to that kind of activity. It is not at all like on Commons (the only other project where I have CU-experience), where you have a suspicion and ask a CU to check it. On German projects (and that is something we can't change) the hurdle is much higher. For those who speak German, you could check the CU-request-page at German Wikipedia to see what kind of information collection is necessary to get a CU ([ http://de.wikipedia.org/wiki/Wikipedia:Checkuser/Anfragen]). So actually the chance to detect a cheater is now much lower than before.
To the suggestion of 'searching a new developer': I don't know how much quality ThomasV produces in his code (comments, format, speaking names for variables/...; bugs are normal, but the amount of bugs in each release is not a good sign), but one thing I know from several years experience: taking over the code of somebody else is no fun at all. Often enough I ended up rewriting the whole code. Getting a second developer to work on the same plugin is a bad idea from my point of view as a developer, even if it is in a second branch (to prevent conflicts). It usually takes months until the first working output gets generated (one that does not cause troubles at zig other places, because you had not yet had the overview and did not know that changing something at this place will cause consequenses in a totally different area). Sorry, but I suppose that Birgitte does not know what developing a working software (not speedily hacking some emergency-tool) includes, because we are having the problem now and not in half a year (just a estimate as I have not seen the sourcecode of PR2).
And we are stuck with PR2. It IS a good idea, and it is more encouraging for those who do the proofreading, because they can do one page now and then later another without a huge text complex. So in the last few years German Wikisource has transfered a majority of its projects to this solution (especially the large ones). Thus switching off the PR2-extension is not an option, since it would break most of our projects and converting them back would probably take several man-months (even with the help of bots). We don't want to get rid of PR2, we just want to be able for everybody to use it, not discriminating a few users who for whatever reason prefer to work without an account. They are as valuable to the German community as registered ones.
Sorry, that got a bit longer, so I will stop now.
Regards, Cecil