Not a lot of quick solutions for mixing up combat spring to mind, but...
- The game features black ink splotches on the ground but they never connected to gameplay to my knowledge. Perhaps splotches could be a source of enemy spawning. Finding and destroying them could stop spawning or weaken enemies. Communicating this might take some intentional dialogue or tutorial interactions and "hunting the black splotch" may only be an interesting distraction once or twice, but it could make flashbangs or flares more interesting if using them highlighted splotch positions. This could add some interesting risk-reward, since being able to find spawns or annihilating immediate enemies could be an interesting choice. Maybe not!
- I liked that there were oases of light that could be used in combat but didn't like how non-interactive they were. Often, lights just break from a supernatural force when you near them. Instead, it might have been fun if a clump of shadow was thick enough to block out a light. You could see through the shadow a bit, like a deep, dim glow, and you could shine your flash light to disintegrate the shadow and fill an area with a sudden blast of light. I like the idea that enemies could then build up a scream or something and destroy the light, so it only works briefly, but enemies can be killed while readying this attack.
- Wake actually features a dodge-to-slow-down-time mechanic, a la Bayonetta, but never does much with it that I could discern. It would have been nice if it created weak points or let you do a lot more light damage than it appeared to. The risk-reward (let enemies get close and attack) is so simple and satisfying that the game could have leaned on this one mechanic alone, just like Bayonetta did, to great effect.
- Similarly, just having moments in an enemy animation when they were extra-vulnerable to light would have been nice. Perhaps a strange sound could cue the vulnerability. Perhaps enemies that lose their shadow shield can attempt to rebuild it, but during this moment, being shined on with light will destroy their corporeal form instantly. This could add some interesting risk-reward, since leaving a guy without shadow for a bit could mean letting you insta-kill them without using ammunition, but leaves them threatening on the field for a bit, and could allow them to regenerate their shields if the window pass you by.
I also wonder if combat always feel less interesting because every encounter begin with the exact same thought: "how do I get rid of its shadow," which is always resolved with light. The story once described the enemy as shadow with a human mask, and taking this idea more seriously might have made combat easier to design, and grittier. This alternative approach would require blasting through a physical barrier (e.g., skin or metal,) to expose shadow. The challenge involved in removing the physical barrier could be as varied as in any game, requiring any number of weapons or tools, and shining light on shadow is instead the finishing blow or a momentary point of weakness. It might allow for a wider variety of enemy visual concepts and intuitive, physical design problems for players.
But it would probably be to costly to retroactively implement, and with uncertain impact. It would probably take a team of designers doing some brainstorms to see how the ideas compared to the shadow-shield method, only earlier in production, and at an unacceptable cost to the story or visual themes. It's just interesting food for thought.