James I think this is what Sam's been doing for years? People may love his sets, or not (personally I love them), but he's always got that battered sales box out wheeling and dealing! (and always very fairly IMO). Top guy and the top 'proper' DJ on the scene I reckon. The right attitude to both the dancefloor and to his tunes IMHO (and not bad on a pension, as he often says! ).
Then again, as I said (tongue firmly in cheek) to him at Prestatyn, I don't need to go and hear him out so much nowadays as there's always some other cheeky monkey out there trying to play his spot anyway...... And maybe that's why the 'ultimate hot-box' idea could ultimately fail. Everyone would end up chasing the same tunes (maybe we all are anyway?). Using your footy analogy, the team with the most cash would, in the long run, probably come out on top even though, at their heart, they've got no 'feel' for our beautiful game. Look at Abramovich... Football fan or business man? Potential long term servant to the game or playing with his new toy? Or does it matter just as long as his mob (oops!) finish top of the pile?
Then again, on the subject of money can't buy me love (or top DJ'dom), whatever happened to Steve Chadwick? Is he still around? (Genuine question)
Basically, I think your suggestion is bang on as far as trying to provide the best set possible every time (whilst taking the needs of the venue into account of course). Play the best records for the situation. Plus I reckon every venue should limit DJ's to just one 50 count box of tunes. It always amuses me when DJ's look like they need a fork-lift truck to bring their box into a venue, and then 20 out of it get played!
Steve