I do not see the "infrastructure" to be here a great challenge.
To some extent I also meant to imply social infrastructure. The site itself mainly acts as a tool to keep track of who is signed up for what, plus fairly typical forum software (similar to liquid threads or any other forum implementation): not so unique. I'm certainly not suggesting that P2PU has the most amazing platform or anything like that (in fact, they are currently in the process of rebuilding it). I'm just saying that it seems like a place to possibly simplify by reusing/combining.
(Just today I learned about a course that will be running on Wikiversity, and I signed myself up for that, for purposes of comparison - and out of interest in the subject matter of course!)
Collaborating with the P2PU and all the other open education projects is extremely important. When the movement is growing (as I hope) different approaches with a similar kind of objectives will benefit all.
I quite agree. One shortfall that I can see in the broader community is that there isn't any particularly well established practices for cross-site or "meta" collaboration. Is there good potential for many of these sites/organizations to work together in a "coalition" of sorts? Admittedly there are many very different approaches, as you say, that should come with the possibility for mutual benefits from collaboration.
Learning from each other without Not Invented Here -syndrome would be great, too. If Wikieducator, P2PU, PlanetMath or LeMill (http://lemill.net/) does something better, the Wikiversity community should do the same.
Definitely important, and I think the particular syndrome you mentioned really should be stamped out if possible!
I'll also add that there may be times when it is a better strategy to do some "division of labour" than to clone features found elsewhere. It's just a tiny wording difference from what you wrote, but it could be the difference between e.g. reimplementing the P2PU systems, or using them. Maybe both approaches should be pursued - certainly both should be considered.