I have to say that although Mixmeister is very good and has a big following, I don't think it will sit well in the MJ UI and it is not the most user friendly of DJing packages (something that should be important as an MJ feature.)
May I suggest that you look at
www.carrotinnovations.com for Virtual TurnTables (VTT) it was actually one of the original PC DJ programs.
Basicaly it main starts with a file/playlist manager (like MJ but not as good.)
It also has a little mixer pop-up window with crossfader etc and two (or more!) jog shuttle pop-up windows for each song with cue points and pitch controls etc.
I think this pop-up ability of virtual mixer and jogshuttles would fit perfectly with MJ's existing interface without requiring any reworking.
As a side note you can buy a splitter from electronics stores (£5)that allows VTT to work with one soundcard and still switch channels in the headphones only!
I will post a screenshot next.
Cheers guys