I think in the context of top level chess, eliminating opening prep is the wrong way to go. And I don't like 960 either for that reason. I think the problem with opening prep today is that there are so many drawish openings and forced draws, constructed repetitions etc. In other words it's just too easy for top players to make a low effort draw.
To make top level chess more interesting I have a handful of ideas that work in tandem.
1. Change the scoring and rating systems so that a win is worth more than two draws. E.g a win is 3 points for the winner, draw is 1 point to each player. Game theoretically this should favour players that play for a win and avoid easy draws. But also modifying the rating system is crucial, otherwise we'll get the same drawmeisters dominating the rating list.
2. Change the repetition rule to be similar to xiangqi(Chinese chess) where repetitions are illegal and don't lead to a draw. This eliminates most of the lowest effort draws right out of the gate.
3. Make the game sharper and more complex. The easiest way to do this is just to remove the concept of castling altogether. Former world champion Kramnik has advocated this, and computer analyses of the ruleset is promising. King safety is suddenly a hard problem to solve in most openings and the game becomes much, much sharper.
4(optional). add more pieces. The best way is Seirawan-chess, a modification of Capablanca chess that adds a knight-bishop(hawk) and knight-rook(elephant) without changing the board geometry and starting position.