Now according to a recently discovered patent (via Nintendo Life), more potential details have been revealed. The patent was originally filed back in 2014, but was recently updated. According to the patent, it describes how the console can actually be broken down further by having certain buttons on the controller removed.
The patent describes how the d-pad on the controller can be removed in favor of additional buttons, meaning that similar to the Xbox One Elite controller, this controller could be customizable and setup according to how a player might prefer. However it is only a patent meaning that Nintendo could just be cooking up some ideas.
Then again, the recent update is rather interesting and certainly lends itself to the speculation and rumors. According to Nintendo, the NX will only be launched in March 2017, but hopefully details of the console will be shared later this fall.