Although the Reader plug-in technology is based on signatures, this is not the right forum to reach people who might have the answer. You need the Acrobat SDK forum.
I should say, though, that all available information is in the first link you quoted, and I recommend you apply immediately because past discussions show that it can take a long time. The application form clearly gives the information needed e.g. "Please provide a full and complete detailed description of the features, functionality, purpose and uses of the plug-in". Be accurate and thorough. Remember that Adobe reject many requests, and do not need to give a reason. Remember that a purpose of the program, arguably almost the only purpose of the program is to protect and encourage revenue and you may have to replace revenue lost from sales of Acrobat. The cost of DRM plug-ins is quoted, all others are by negotiation (well, Adobe quote you a value, I don't think there is much scope for negotation in reality).