ambitious midi table plans

Hello everyone, I've embarked on a rather ambitious plan to build a midi controller, but not of the regular type.

What I am looking to do is to take an ikea expedia 2x4 bookcase, (the kind most of you use) and turn the top into a large bedroom DJ and producing station. I will have drawings up soon, but I would like to have a mixer, 2 decks (set up for 4) a samples section, fx, loops and hotcues all built into the surface of the table. I am also looking into putting an 8x8 grid of arcade buttons to launch clips in ableton as well.

My goal is to have 2 separate "controllers" built into one, where one person can mix tracks, while the other runs ableton (2 separate laptops) but with one audio out running to the amp/speakers.

My question for all of you DIY controller builders is this: what features do you all like to put into your controllers? I am looking to add a lot of buttons, faders and knobs, as I know what I want, but as this is a large project, and I don't plan on modding my build later to add more buttons. So what do you guys see as essential features that you use, outside of the standard 2 decks and a mixer setup? I plan on mapping this to traktor and ableton.

Once I have the drawings posted, the idea may make more sense, however it has all been inside my head the last couple weeks.