I like the fact that the Biohacker can go Wisdom or Intelligence, because it really opens up their build ideas, and allows some interesting multiclass combos with Mystic or Mechanic, but the option needs to be fleshed out more before it is mission-ready.
I ran a level 4 Dwarf Str/Wis biohacker in Beacon Code Dilemma over the weekend, and I was really underwhelmed after playing a Ysoki Dex/Int Biohacker previously. While my rolls certainly didn't help (no attack roll with the painclaw over 5), I think the worst thing was that I wasn't very helpful to the group.
Instinctive Biohackers get their Wisdom bonus to Life Science, Medicine, and Physical Science. That's all fine and good, but one could argue that the sciences should be the Biohacker's baseline. Conversely, the Studious Biohacker gets their Intelligence bonus to Perception, Sense Motive, and Will Saving Throws. That's nuts. They are already good at all of the important Intelligence skills (including Engineering, Culture, and Computers) and get the general purpose adventuring skills of Perception and Sense Motive as well. The Instinctive Biohacker is comparatively mediocre in the applied technical skills and the other Wisdom skills that they would be good at, Survival and Mysticism, aren't class skills!
In the adventure, the Technomancer did as well or better than me at science and the two Operatives did better than me at... well, everything else.
I think my biggest problem was that I had 60% of the skill points of a Studious Biohacker of the same level. Not investing in Intelligence severely hobbled my toolkit. Not having many languages (I speak... Common and Dwarvish...) actually made me feel kind of hopeless when dealing with the multicultural Starfinder universe.
Furthermore, the Spark of Ingenuity for Instinctive Biohackers is kinda garbage compared to the Studious Biohacker. Dazzled is just not very powerful to add compared to being able to mix two different Counteragents for twice the duration (Off-Target is twice as good, Fatigued is that and more, don't even get me started on Confused or Sickened), and removing Dazzled, Fascinated, or Shaken is pretty corner-case, especially since a lot of those conditions only last for a round or two anyway (and Fascinated can basically be removed by observing ANY hostile act OR being shaken as a standard action... adding Fascinated there literally does nothing any ally could not do for free). Further, Treat Condition, a level 2 Theorem, removes Shaken, Sickened, or Staggered several times per day... which means the only thing that Instinctive Spark of Ingenuity is best at is adding or removing Dazzled. Meh.
So... I think they need work.
Scientific Method for Instinctive should be roughly equal to Studious. That means two skills (let's say Medicine and Life Science) and an important Intelligence modifier, something equivalent to a Will Save for Wisdom. The obvious choice is Skill Points per level. Studious Biohackers are skill monkeys that beat Mechanics and rival Envoys, other than in their Insight bonus skills. If you're not going to give them their Wis bonus to Skill Points per level, then we'd need to open the skill bonus to more Intelligence skills, adding back in Physical Science but also throwing in Engineering and/or Computers... and I would still want my Wisdom bonus to languages at first level and/or adding Mysticism and Survival to Class skills for an Instinctive Biohacker. Honestly it makes sense, because the Instinctive Biohacker isn't some lab tech with book learning... they should be out in the wild picking herbs and testing out old wive's tales & legends.
For Spark of Ingenuity... I kinda like the idea of the Instinctive Biohacker being able to heal with Restoratives. So take away the ability to add Dazzled to an injection and simply give the ability to add Field Dressing to their Spark of Ingenuity injections, or at the very least, Fast Healing 1 per 3 Biohacker levels for the duration of the Restorative.
Other assorted Biohacker stuff:
Still don't like the names of Restoratives and Counteragents. Should be Boosters and Inhibitors.
The Custom Scanner should serve as an Advanced Medkit at 5th level.
My dwarf melee biohacker really would have enjoyed a Theorem to inject himself as a Move action rather than a Standard action. Self-buffing could be made, with some investment, a little easier on the action economy so they can shoot up and then contribute to fights better. Basically like an Envoy using Get 'Em! and then shooting. Or perhaps more like Clever Attack where they can self-buff and attack with the same Standard action.
I find myself always taking the Quick Load theorem because the action economy of loading a weapon with an injection, especially in melee, is rough because positioning is king. It should be a baked-in class feature by 3rd level or so.
Similarly, it is hard to pass up Painful Injections for that ever-elusive bonus damage. The theorem needs to be clarified on just what the damage "stacking" means (is it only once per round, once per combat, or once ever?), and what opponents are susceptible to it... does the damage have the "pain" descriptor like a Zon-Kuthon divine blessing attack? Does a painful injections effect hurt undead? Constructs? Basically make the damage clearer and more circumstantial so not every Biohacker takes it to make up for the fact that their specialization in injection weapons is only at half-level.
I would like to see Field Dressing be a little more flexible. If you don't add it to the Instinctive Spark of Ingenuity like I suggested, perhaps make an 8th level Theorem to be able to add it to an injection, meaning that you can shoot healing at an ally with a needler without buying a serum. Maybe make it a Resolve ability?
I'd like for ranged restorative injections to be able to subtract the willing target's Dexterity modifier from their KAC instead of adding it because they would lean into it rather than dodge away from it. This should apply to anyone shooting a healing serum or medicinal, though, not just Biohackers.
Preaching to the choir, brother!
They're aware of the problem and I think its something they said they would try to fix
Giving the Instinctive Biohacker the ability to use Restoratives on himself as a move action would be pretty cool, and very different from the Studious abilities.
Also, I think rolling Will Save on Intelligence is an extremely bad idea. Pathfinder made some of these switches in attributes, too many of them, and ultimately, you could have saves, AC, Knowledges and main spell attribute all on Charisma. It was pretty ridiculous.