Profession - Humans commonly spend long times studying and preparing for a specific type of job. Thus, when buying a 'History' trait, it does not cost a Trait Point. Additionally, stat bonuses gained from History traits are increased by 1+ Scaled SAN/20.

Quick to Master - Humans live in a world where they must constantly adapt to situations and circumstances they find themselves in, which makes them more versatile than other races. They gain +2 class skill points for every class. Additionally, their skill pool size is increased by 2 + Scaled SAN/10, letting them equip more skills at once.

Divine Eyes/Eyes of Elimination - I'm wary of messing with this for better or worse but it's the most obvious pick for giving Humans something that scales with SAN. It's already a bit of an investment to qualify for on builds that want to actually cast EoE instead of only cheesing you with Divine Eyes. Perhaps if Divine Eyes was adjusted but as it stands it'd feel either way too overbearing to buff with SAN bonuses or too punishing to require SAN to use effectively if it was balanced around having SAN to use at its current efficacy. At most, I could see it being a SAN requirement instead of WIL requirement to buy the Divine Eyes tree for now.

Humans are pretty OK as it stands, and getting extra stat points is pretty standard for some SAN scaling benefits ala Kael instinct, so getting 6 stats (8 if you're lispoolian and hard dump SAN) for 38-45~ points invested (accounting for APT bonus) feels pretty fair to me. The skill pool bonus is largely unneeded nowadays but the alternative is more class skill points and that feels a bit much. Having SAN act like a 2nd WIL for skill pool seems in line for Humans.

Homunculi Physique - An artificially created lifeform. Received healing reduced by 10%. HP per point of VIT reduced by 1. FP per point of WIL increased by 1. HP/FP per point of VIT/WIL is increased by Scaled SAN/20.

Salamandra Flame - Can just get Scaled SAN added to its damage on top of everything else. For a total of 100% SWA + 100% Fire ATK + 100% Scaled SAN.

Wyvern Assimilation - Infused with the blood of a wyvern. 30 + Scaled SAN% status resistance versus Poison.

Salamandra Flame Arts - 

Explosion - Dunno what to do for this one that's sensible. Possibly lowering the 50 damage requirement by something like Scaled SAN/2? Or just straight up Scaled San if you want to get crazy with it. Honestly if someone is building SAN and actually critting they deserve the fireworks at that point.

Poison - Make it scaled on SAN/2 instead of GUI and cap it at 20/25. You have to deal a significant amount of damage to even have a chance of landing this it can afford to be higher than LV 15 poison, and you're sacrificing the more consistent Explosion for this. Additionally, another possible change is to have the infliction rate scale with SAN. Something like adding Scaled San/10 to the 5% of your inflict per 10 fire damage. So 50 Scaled SAN would make it 10% per 10 damage instead.

Purification - Easy. Cooldown reduced by Scaled SAN/20.

Amalgama Mutation - There are a lot of different abilities here to consider even if a lot of them are reflavored versions of one another. I think it best to leave the unique class of mutations alone given how powerful they are already, and provide bonuses that are equally effective regardless of what you roll.

With that in mind:

Spell Mutations - Either adding Scaled SAN as damage or amplifying the bonus vs the races it has by Scaled San%. The race damage bonus for these almost never comes up since 10% is negligible for an ability that's 100 SWA/100 ELE ATK scaling. Odds are they'd do more damage casting something else if they're building for Attune Grudge even if they rolled the correct spell, not to mention it cannot be double-tapped due to having a 1 round cooldown, so doubling up on the two being problematic is unlikely.

Support Mutations - These all vary between HP/FP regen and curing status ailments so it's difficult to provide a blanket buff for all of them. My first thought would be reducing their cooldown by something like Scaled San/20 rounds, so you could lower them from 5 round to 3 round cooldowns. I'm unsure if also providing a numerical buff from Scaled SAN on top of that would be overkill. Jorg is already pretty good for self-sustain but it is certainly an outlier.

Please for the love of all that's holy let their own racials heal them fully. Matil's 120 at level 60 gets cut to 108 by default as it stands.

With that aside out of the way: The healing mutations could afford to have Scaled SAN added in full. It's a piddly amount with the cooldown you'd expect on a healing skill. Otherwise the cooldown reduction should suffice for the status ailment recovery mutations.

Status/Element Resist/Weakness Mutations - These are tough since my first thought is to modify the resist values by Scaled SAN/2, but Dev already went already removing every instance of that from prior racials to make resist stacking more difficult. These will likely all be left as is, unless Dev decides otherwise.

Chimera Evolution - This is a lot to cover much like Amalgama Mutation, except every mutation's only similarity is the +5 ELE atk bonus it gives. So offering SAN bonuses will be on a case by case basis for the evolution skills Chimera gets. I'll go over them all individually.

Chimera's Dragon Wings - Unchanged. They don't even exist in Korvara and their biggest benefit is gaining the race-type itself. I can't really think of anything reasonable to have SAN provide without drastically altering the skill.

Chimera's Hot Blood - Intense body heat flows in the Chimera, protecting them from the cold. Gain Fireblood racial type. +5 Fire ATK. Frozen status effects you are inflicted with have their LV reduced by half (or 50 + Scaled SAN, whichever is higher). 

Chimera's Fish Tail - Unchanged. Similar case to Dragon Wings, not much here to modify. The flooded water penalty negation is enough as is.

Chimera's Stone Stare/Venom Glands/Starlight Eye - Hard to modify since they're granting an existing skill rather than it being its own thing.

Chimera's Tyrant Paws - Monster-like feet allow the Chimera to traverse the snow. Gain Iceblood racial type. +5 Ice ATK. While you have no Legs item equipped, you do not trigger Ice Sheets, and your Kick skill deals Ice magic bonus damage equal to half of your character level + Scaled SAN/2. Makes for a good alternative to bladed soles for focusing on higher, single-instance damage. Unless this actually applies to rapid kick in which case uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuh maybe not.

Chimera's Agile Flexor - Powerful leg muscles grant the Chimera insect-like agility. Gain Insect racial type. +5 Lightning ATK. Increases Kick's knockback by 1. Additionally, increases damage of kick skills by 10 + Scaled SAN/5. For posterity the +10 is base, I just reworded it. The damage increase is middling anyways but I don't want to go any higher than doubling the bonus here.

Chimera's Fierce Grip - Small nubs on the Chimera's hands allow them to get a painful grip on enemies. Gain Kraboid racial type. Grapple deals Pierce bonus damage equal to half of your character level + Scaled SAN/2 which can critically hit, dealing double damage. Same case as Flexor, pretty unremarkable damage but this shouldn't turn into Painful Grip. Comes kinda close if you can crit but at least you have to crit to see numbers like that.

Chimera's Shark Fangs - Unchanged. Like the tail + wings, nothing here to modify since its main draw is removing the physical stamina cost of eating corpses.

Chimera's Accursed Claws - Likely unchanged. These are one of the few good things Chimera has going for it even if the price to pay is steep and you only really benefit from this if you're committing to making a build centered around Grudge Claws. Amplifying the on-hit Dark damage's scaling by Scaled SAN/2% is a thought.

All Mutations - Possibly having Scaled SAN/10 elemental attack added according to the element being boosted.

Honestly I believe it'll take more of a total overhaul of Chimera to address its issues so all these minor changes may end up being irrelevant when/if that happens. Until then these might help tide Chimera over, combined with the change to Homunculi Physique suggested above.