To help in the discussion of the ASL/English wikipedia I have made a sample (http://simple.wikipedia.org/wiki/Clerc). The hand icon there is there to indicate the paragraph is signed. Click on the number one after it to go to the page with the signing that is housed off the Wikipedia site. The deaf adults and students who have seen this are ready to start building more as they see it as a very valuable and accessible tool for acquiring information.
While it is possible to use simple Wikipedia to build a sign augmented simple wikipedia there are several problems. One the word "simple" can have a negative connotation," simple" meaning "not smart" as in Simple Simon. That would infuriate many in the deaf community and doom the project. If videos were housed on each users individual server then a person who wants to change the video that does not have access to that particular server would be unable to do so thus defeating the goal of wiki.
Videos could be stored on the Commons and linked to from the English text page but the video file size limit would need to be increased dramatically from 2MB. The sample video in the link above is about 1.5 minutes and is 16MB.
Making Wikipedia able to handle video will make it more up-to-date. Text and pictures were top-o -the-line in the '80's.
To reiterate an earlier point. ASL is a natural language and deserves a Wikipedia like any other natural language. The users of ASL are bilingual in ASL and English to varying degrees (some totally fluent in both, most more fluent in only ASL) and the languages influence each in the deaf community. ASL has many signs borrowed from English orthography. There is no common ASL orthography. Attempts at using SignWriting and other orthographies have not caught on even after 20 years.
Making an ASL/English Wikipedia will provide the deaf community particularly students a powerful learning tool. An encyclopedia is a learning tool, not simply a collection of articles.