Disclaimer: I am a big Wonder Woman fan, and I do not want to change the Trinity or to start a flame war. I understand the importance of Wonder Woman in comics and other media as a feminine icon, and this article is not intended to be a slight against Wonder Woman. This is a forum for peaceful dialogue.
Something that I found interesting circa 2011 was all of the talk about how Green Lantern should replace Wonder Woman in DC's Trinity. I argued against it for a few reasons, mainly for the fact that Green Lantern was a science hero. You see, I believe that there are thee ways a hero can have power: genetics (Superman/Captain America), technology (Batman/Iron Man), and magic (Wonder Woman/Thor). Each of these should be represented in the trinity, so if you want GL to be in there, then he would have to replace Superman, which shouldn't happen since Superman is the first superhero. Also, which Green Lantern should replace Wonder Woman? None of them is as well known as she is. All of this replacement talk ended after the Green Lantern film flopped, so I feel like I was on the right side of history.
But now, I'm here to start it all up again! Except this time, I'm going to say that Aquaman could replace Wonder Woman symbolically in the Trinity. By symbolically, I mean he could be a better fit for the trichotomy needed for a legendary group like the trinity. You see, Wonder Woman is not the best symbolic fit in the group because there's not easy iconic way to describe her position. Superman is Light. Batman is Dark. And Wonder Woman is? Just right? In the middle? The toke female? The Amazon? None of those really juxtaposes against light or dark well.
On the other hand, there are several iconic abstracts that Superman/Batman/Aquaman could be broken into like Zeus/Hades/Poseidon or Sky/Underworld/Sea. There's also Greatness Thrust Upon (Superman), Greatness Achieved (Batman), and Greatness Born (Aquaman). You could break them down according to Max Weber's three types of authority: Charismatic/Superman, Rational/Batman, and Traditional/Aquaman. And if you look at their color schemes, you can see that they are more different than the current Trinity. Wonder Woman and Superman wear a lot of the same colors. On the other hand, Superman, Batman, and Aquaman have one color in common (Yellow), and two personal colors (Red/Blue, Black/Grey, and Orange/Green). Their names are alphabetical A (Arthur), B (Bruce), C (Clark). They have the three types of story telling found in pulp magazines and comics: Sci Fi/Mystery/Fantasy. They have the three power origins (genetics, technology, and magic). All three come from families with power (House of El, House of Wayne, and House of Atlan). All three date back to the golden age (1939/Superman, 1940/Batman, and 1941/Aquaman). These three heroes have had more sidekicks of both genders than any other hero. One grew up in a rural area (Superman), one grew up in a suburban area (Aquaman), and the other grew up in an urban area (Batman). All three have human archenemies (Lex, Joker, Manta). In my opinion, these three are as great as a symbolic trinity gets.