Many moons ago Brendan over at Necropraxis wrote a very smart blogpost called Overloading the Encounter Die. Marcia B. of Traverse Fantasy took the concept, expands it a bit, and remediates it into a threefold pamphlet called TURN. Since both original post and pamphlet are super short, I will not summarize them here. Although I found Brendan's idea to be very good at the time, I never implemented it. I'm not sure why. But in pamphlet form as TURN, I find it much more compelling. As in, I want to make it standard for my next dungeon campaign.
Some ideas just need the right packaging to speak to some people, I guess.
Traverse Fantasy also has a restatement/reinterpretation of OD&D called Fantastic Medieval Campaigns, but I haven't read it yet. Also, I discovered while writing this post that Marcia B. has a Traverse Fantasy blog and this post is an absolute winner.