This game takes like 8-12 hours, but if you do it in person, it just FLIES by. I was too afraid to take a food break or even a bathroom break because I didn't want to be out of earshot of everyone else so they could scheme against me. We had 15 minutes for planning each turn, and that never seemed like enough. You want to talk to everyone, sometimes including one person, then again after that person leaves to talk to…
I found the best Diplomacy framework is a hard 15 minutes/turn limit. After 15 minutes, your moves are down on paper or they don't happen. This yields a 4-5 hour game.
By "best", I mean, "it's fun, it's intense and it's done". I see a lot of variations being described along with notes they became intolerably intense for people.
Which is to say, this isn't a framework that needs help to be made more engaging. Keeping the excess-engagement genie sometimes in the bottle is more the challenge here.