I like the idea of having someone else pick your tracks. I don’t actually sit there and think of what goes with what. I pick songs in the same key and just kinda go to town. Something eventually just happens. That’s how I found out that Mumford & Sons goes great with Wolfgang Gartner. HAH! I ended up producing a mash-up of the two tracks, which sounds awesome and people love it! I’ll send you the link if you ask for it.
Also, I noticed when I was doing all my DJing this summer, taking requests can also bring about a number of unknown or UN-thought-of combinations. If I had a track someone asked for, I would move into that key, then lace some tech-house under it, and whamo! Awesome combination. Luckily, I was recording all those sets. Listening back to them has given me more mixes for my weekly DJ broadcast.
Great info OP, thanks for sharing!