Even though A Good Day to Die Hard has turned out being a HUGE misfire, I'm still actually up for a 6th movie ... If they get good writers, good actors, and a good director.
Die Hard has been one of my favorite movie franchises. This new movie is the ONLY one I haven't enjoyed (and yes, I even enjoy Die Harder and Live Free or Die Hard; get over it). I want this series to end on a high note.
This is what I want for the next Die Hard film:
1. A better director. People have been throwing Shane Black's name around, and I wouldn't be opposed to that at all. At the very least, we all know that the dialogue would be the opposite of what we all just saw in the fifth movie.
2. A better villain. Pick a good actor to do it, too. Christoph Waltz was mentioned in the OP. He would be awesome. Javier Bardem proved himself to be a show-stealer as the villain in Skyfall ... I could see him going up against McClane, too!
3. Make McClane vulnerable again. In the first Die Hard movie, walking on that glass slowed him down considerably, which was a great way for the audience to become attached to the character and the stakes that were at hand. Even in Die Hard 4, McClane slowed down and got roughed up by the end. In Die Hard 5, McClane was almost entirely impervious to everything, even radiation poisoning. LAME.
4. I want to see Holly again. If the 6th movie is going to be the last, then at least have these two reunite. They don't have to completely get back together, but c'mon. Let us see Holly (only if they get the same actress, though)!
5. Don't let Bruce Willis pick one of his buddies to write the screenplay. Apparently, Skip Woods is a good friend of Willis'. Welp, it didn't work out so well, now did it? I love Bruce Willis, but it usually doesn't work out if the actors get to hand-pick everything involving the film.