Hi Jay, apologies for the long delay in answering your post. Ironically I've been working flat out designing just the type of systems that we've been discussing - so getting people interested isn't my problem at the moment!
Vis a vis the logistics - two scenarios come to mind: One is that we can gradually incorporate more and more eco-friendly technologies as clients want to have lower impacts on their receiving environment. For example in my work, many clients come to me because the local municipality demands that they meet certain environmental standards and they just want planning for their house.
Technologies such as Swedish urine diverting toilets and the Swedish Aquatron separator are both possible to incorporate into a standard sewered system without really letting the users of the toilets know that there is state of the art humanure composting going on down the line.
Also within this gradual scenario is a greater development of P removal technologies from conventional sewage treatment systems, which is happening in Europe - albeit slowly.
The other scenario is that N and P is suddenly and dramatically limited - whether by peak P (which is on the cards anyway) or by an international carbon emissions agreement putting the N-fertiliser business on a dramatically less stable business footing. Cap and Share from Ireland's Feasta (Foundation for the Economics of Sustainability) is one such programme - recently highlighted in Naomi Klein's Beautiful Solutions page (http://www.feasta.org/2016/03/30/capglobalcarbon-has-been-accepted-as-a-beautiful-solution/
Personally I'm not too worried about a carbon source. I've been designing willow facilities in the Irish context since 2007, in collaboration with Danish company Centre for Recycling, who have been at it for about 20 years. These are zero discharge systems whereby septic tank effluent is pumped into a plastic lined willow bed of c.6m x 35m x 1.5m deep. The willow mop up all effluent and all rainfall over the course of the 12 month cycle. Willows are coppiced on a three year rotation basis.
If we take a multi-pronged approach to this issue, then some people will want a willow system (those with no legal way to discharge to ground or water for example), some will want a dry Jenkins' type system, some will want the standard town sewer (but even here there is a move towards using willows to mop up more N and P from the final discharge). With all that willow being generated there is an abundance of carbonaceous material available for balancing N.
It takes hoop-jumpers to change the laws, so I applaud the Eco-village people that you describe. One of the things I do for a living is basically about wriggling through the existing legislation to find ways to allow clients to be more eco-friendly. And trying to get that legislation changed where necessary. I'd love to make it out to Vancouver Island to visit and compare notes!