Hi, Ben -- four comments!
First, I think we are creating very few new pre-1500 profiles, and when we do there is a very high bar of credibility required. Only pre-1500 certified people are authorized to create new pre-1500 profiles, so I don't think there is an issue of the use of tertiary sources like Marlyn Lewis's site. I wouldn't create a profile if I had only Lewis's say so, and if he referenced Richardson, I'd go to Richardson directly; even if you don't have Royal Ancestry, Magna Carta Ancestry contains a lot of the same material and can be found online.
Second, there are a huge number of existing pre-1500 profiles with no or rudimentary sourcing. These are an ongoing effort to gradually improve profiles, and they are a collaborative research effort. So if I encounter a profile that only has material from a Gedcom linked to an ancestry link that no longer works, and if I find material on Geni or Lewis's site that can help make sense of this person, I add it. With inline sources so that you know where every single fact came from. That makes it a better profile than it started out. Sometimes I find profiles with a birth date in the data field and nothing in the bio, and sometimes I put the date in the bio with the citation "Wikitree Data Field, not otherwise sourced." Is that appropriate for a finished product? Absolutely not. But now you've got a flag that at the moment you have no clue where that date came from and it's high on the list to get better data as soon as possible. But maybe you only have an hour to work on that profile this afternoon. You spend two hours on a profile and you leave behind something that makes more sense and any reader knows where the facts came from and therefore which ones are likely to be unreliable and need to be replaced. It's nice to aim for a finished product, but the fact is all we ever do is create better and better drafts with the hope that someone else will come along and make it even better.
Third, if a pre-1500 profile is Project Protected PPP it's probably part of the Euroaristo Project or one of its sub projects. If you're working within those project parameters the only thing a PPP prevents you from doing is changing LNABs and link relationships and merging the profile into a higher number than it already is. So if you see a raw profile that obviously needs work, the PPP doesn't mean that work on it is rejected, simply that the project doesn't want the profile's LNAB changed or merged without consultation. So I don't think PPP is the barrier that you are experiencing.
Fourth, I experience some consternation over your use of the word "allow." Yes, there are things that WikiTree doesn't allow, and there's an advantage to keeping these to a minimum. I take my turn for an hour as a Ranger to monitor WikiTree and make sure that non-allowed stuff isn't happening. But WikiTree is a volunteer effort, and it is one in which everyone is constantly learning. I hope every single person who has been on WikiTree for a full year or more is a better genealogist today than they were a year ago. But we're operating on a continuum. Forbidding people to use a particular site, or to use material from that site that they felt helpful, as long as its source is properly cited, slows down both the individual learning process, and also WikiTree's efforts at "continuous quality improvement," to borrow a phrase from another field.
