Hello Rod,
I'm not as involved with the Friends project planning having taken a new job and spending a lot of time in far away places. I'm not sure the plan is entirely written down as because of some unfortunate circumstances, things have been changing. Basically 053 is pilot project and is progressing in the Antonito CRF. I haven't heard any updates to the overall plan since the property was acquired in Chama, but it wouldn't surprise me if some of the the follow on passenger car work was dependent on that facility coming online.
I can remember very clearly when the 1st car (remains) were acquired many years ago, John Bush told us to the effect: "rebuilding a passenger car will be a bit more difficult than painting box cars". As I found last week, things that were relatively simple on 0579, are an order of magnitude more difficult on 053.
My own opinion (and may or may not be shared with others) is that these projects will need us to be more creative in how do the work; as you suggest it's going to take more than the current program to get the work done before anytime in the next 20 years. Hiring a full-time restoration expert may be one alternative, but that will obviously require a good source of funding.