The problem with this one is going to be submerging the expository world-building into in-character observation. I have two points of view to play with, at least. They have significantly different viewpoints on the interactions, which is very handy. Almost as if I planned it that way! I need to do non-trivial exposition, too. I find the standard ABO dynamics kinda tedious, both in the way they erase women completely and how they set up strict social hierarchies. I'm more interested in the many other ways a biology like this would express itself in culture. And change the dynamics of our little group of Scoobies.
Standard science-fictional stuff.
Here's another piece of meta that claims every ABO story has at least 3 of the 5 elements listed. I am hitting the first two right on the money, am ignoring the third (knotting), and am gracefully pretending that nobody mentioned the fourth in my hearing. It seems completely unnecessary to me, though hey, if it's your thing no problem. Soul-bonding I love, but it also seems to me to be unrelated to this trope. So I'm only hitting 2 of 5. Oh well.
At its core, the trope for me is: Humans can go into heat. Specifically, humans capable of becoming pregnant go into heat. This has a pheromonal effect on the mature adults around them. Loss of control results. Hijinks ensue.
Also, pack dynamics ensue. But ones specific to humans. Invented by me, because I see no reason to follow all the existing rules with the trope. And, um, to be honest, I haven't actually managed to finish reading a single existing story featuring it. The, um, self-lubricated butts squick me. There are some weird things going on with these projections of aspects of female sexuality onto male characters that I cannot even begin to understand. Not my kink.
Loss of control: I can work with that.