I think you are on track with most of your points (max potential energy = least entropy, and most ability to do work) and (max entropy = no ability to do useful work = equilibrium). complexity is max somewhere between these two extremes - much before equilibrium occurs).

Let me sharpen it up with an example. We have to introduce the notion of a 'macrostate' consisting of many 'microstates'. If you can think of a slot machine in a casino with five reels spinning - the macrostates are "win" and "lose". there are only 5 possible microstates associated with "win" (where all five reels show the same picture) - but 120 possible microstates associated with "lose". When the slot machine was first at " factory setting and nobody played yet on the floor of casino", you can imagine our surprise if you find the reels all lined up to the same image. It's a surprise, but it can happen (this is the state our universe was in - with only minor quantum fluctuations but otherwise smooth and homogeneous). but once the machine gets used - things start to get interesting. occasionally someone wins the jackpot with all five pictures lined up. but mostly it's the casino taking the winnings because of the setup (120 possible states out of 125). unfortunately this is as far as the analogy goes. but complexity arose spontaneously where things were interesting, but not at the very beginning (homogeneous, least entropy) or at the very end (also homogeneous but max entropy) but somewhere between the two extremes.