Yes, I already have plans for this. However you will need to include a chip to send the ID bits to enable alternate mode, this can be programmed with an embedded kit such as Arduino. One of the issues is that the USB 3 spec was updated recently and includes a lot of changes and new requirements. It's almost getting like US tax code how convoluted it is.
There are some things specified that probably aren't that important for homebrew stuff and can be ignored or dealt with later. Things like ordering of wires within the connection cable, etc.
(I was going to build a simple MDP adapter with power charging.)