EDIT: THIS IS NOW IN A NEW THREAD TITLED "CYBERNETICS"
Imagine you have at the end of your prompt a little white 'o'. This represents your bio-augment.
Each time you take a hit it either turns red, green, or remains white. If it turns red, it means your augment is vulnerable to theirs. Green means it's strong, white means it's neutral. The strength/vulnerability then affects the damage you take. So if your augment is vulnerable, you take an extra 10% damage, if yours is strong it means theirs is vulnerable, so they take an extra 10%, be it melee or magic.
Now imagine you have three augments available to you to place in your augment slot: fire, water, and leaf. Fire is vulnerable to water, strong against leaf and neutral to itself. Pretty self-evident, I'm just using them because they're easy to follow, they could be anything. The key here is that you can swap them at any point. So based on what you have and whether it turns red, green or neutral, you can guess what your opponent has and swap your augment accordingly.
Now imagine there aren't just three possible augments, there are say 10, each with a strength and a vulnerability. Now when you take a hit and your bio-augment turns red or green you don't know immediately what theirs is - at best you can narrow it down and guess between two or three.
Now imagine you don't just have one 'o' at the end of your prompt, you have three. Maybe they correspond to speed, damage and accuracy; maybe you have five and their aggregate vulnerabilities determine the percentage change in your damage taken, whatever.
.. Maybe you have three 'o's affecting damage, speed, accuracy, and each one has a sub-realm that can hold five augments and instead of turning red or green you get a value from 1-100 to represent that subset, where 1 is total vulnerability and 100 is perfect strength. I don't know, the possibilities are endless
The point is that regardless of how intense it is, the system is dynamic. So now if you just sit there spamming behead or fireball all your opponent has to do is work out your augment setup and adjust, and suddenly you're getting rolled unless you can also adapt.
I wouldn't like to see augments with actual stats attached to them (IE this one has +5 against water and that one only has +3 so this one's better), I prefer the idea of simple types with a strength and a vulnerability so there is no perfect set like there is with equipment. It should always be dynamic.
I also like the idea of letting builders create their own types and choose the strengths and vulnerabilities, so I could make a purple augment that is strong against fire and vulnerable to jacaranda, as long as it doesn't have more strengths or less vulnerabilities than anything else. Then you get trends in which random augments from far away make for unusual setups that are hard to pick, or are strong against popular types.
I think that's enough for now. Work in progress, help me out