While I am and always have been a strong supporter of language and dialect preservation, I have some concerns about starting Wikis for "languages" virtually indistinguishable from one we still have limited support for (not to take away from our terrific es: contributors in any way -- quite the contrary).
Sr. Quiles, assuming a knowledge of Spanish consistent with a few years of casual study focusing on Latin American dialects, would I be able to distinguish between Castilian and your Extramaduran? You've already stated that the two are mutually intelligible; past consensus has nixed dividing efforts among mere dialects of a language, as with British and American English, Portuguese and Brazillian Portuguese, and the various dialects and languages of Germany. What distinction does this project merit to warrant a separate Wiki?
I'm not the deciding authority, by any means, but I'm sure I'm not alone in wanting answers to these questions.