The patent for "Expandable Control Device Via Hardware Attachment" deals with a series of control options. The patent seems to suggest the ability to join two motion controllers together lengthwise, or in an H-Shape. A unique secondary controller attachment may finally solve the missing analogue stick issue, while other potential add-ons show a maraca and flashlight add-on.
Interestingly, the patent also includes a biometric reader attachment, which includes a "thumb reader used to validate the identity of the person holding the controller by analyzing the biometric data provided by the attachment." Dude?
Further add-ons include swappable control faceplates and microphone attachments.
As a patent, there's no real suggestion any of this stuff will ever see the light of day but, dude, what? This stuff is crazy.