I'd bring back Parasite Eve as an intense, survival horror action game. Dive deeper into biology, science topics and more psychological. I wouldn't exactly remake the original; more like a reimagining of the book's concept to allow more freedom for pursuing different themes. A private investigator, a detective who's exposed to this phenomenon and slowly unravels the conspiracy.
Mechanically, I'd aim at something akin to an over the shoulder camera, with scarce resources (ammunition, curatives) and the Parasite Energy. Parasite Energy would have more risks if you exploit it, kinetic abilities (like Mass Effects) hinder your stamina and abilities like igniting foes would damage your stress level if abused.
The stress level, for now, conceptually would be in a more thematic addition, as using these parasite powers means it takes over you, it causes pain, headaches, nausea, etc; you are not Aya, you are not some superhero with 80 handgun ammo. Having an assortment of curatives that helps with these status effects. Letting them linger can change not just the moment to moment gameplay but how the story unfolds.
The RPG elements would be moved outside of combat, Parasite Energy would have it's evolution, but only if you use the abilities more often not because of an experience bar. Using certain skills could potentially unlock other paths, akin to a DNA schematic.
Dialogue choice and branching paths are a key part of the experience, as using certain PE skills and your detective work open certain scenarios and dialogue;
Enemies would be ferocious, disgusting and would force the player to make hard decisions. Taking a note from the original, and how certain animals evolve; I'd like to imagine how the APEX predator version of that animal would behave. What sort of skills would be most suited; like fighting a mutated giant rat would be a waste to use ammo as they're quite fast but a kinetic ability, like throwing could deal with it easily at the risk of stress.
It would be somewhat linear, scenario to scenario but you can revisit certain areas if you missed anything. A police station as the main hub with options to upgrade guns.
and it has to be a brutal, as disgusting and gory as the M rating can allow it to.
and the main character would look like Penelope Cruz in the 90s but a lil more pale, black hair but that's just my prostate thinking for me.