I'm so sorry. I never got any notifications about your message. Regarding magic systems. the game already has one in place.
Wizards are ones who study magic and use the mana within their bodies.
Sorcerers use the mana around them and receive their abilities from patrons, items or inherit them.
Witch/warlocks manipulate mana from another dimension and get their power from these other realms.
Each one is capable of learning certain types of magic and could also be broken into a subclass. There aren't any guns or technology in the game, but a few things could be substituted for similar results.
Your character Astra can be half of an artificially made race. The restrictions for artificial races vary because their body composition can be made of many different things. She can be a high ranking member of the clerics (light magic sorcerers) and use special enchanted gems that can be placed inside the artificial part of her body for various effects.
This could range from druid sorcery being used to create a wooden sword, light barriers, fire blasts from finger tips like bullets from a gun, etc.
Psychoborg would be a warlock with a special gauntlet (I have gauntlets in the game as weapons). He can use the many different forms of warlock magic by switching out a jewel (shadow, blood, etc). The gauntlet could be the severed arm of a demon that can take on different forms like a shield or blade.
Thing is my game has the player as a blood parasite (red slime like creature) with the ability to possess different bodies and essentially collect power. Most missions are actually just tasks assigned to other characters that you complete while controlling that character. So your side quest story line is very possible.
Let me know your thoughts.