adding extra skill or 3 tools, languages or weapons per intelligence bonus seems like a good idea, but again, then you will have; why is wizard and artificer getting more skills than anyone else as they are now double dipping with Int increase.
partially goes to EK and AT.
IMHO, beast way is to balance out 6 saves that ALL have more or less similar power of effects to defend from and similar number of them.
I had an idea IMC for a boost from INT, and this was the first feedback I got. "The rich get richer." Which I think is kinda of a BS answer because looking at my PCs, the INT scores are 8, 10, 8, 10, 8, and 10. No wizards or artificers; a fighter/rogue (INT 8 arcane trickster, no less!), warlock, cleric, rogue/druid, ranger/barbarian, and bard [in that order of INT scores]. No one felt the need to have a positive INT score because why bother? If there had been a wizard, he would have INT 18, because of course he would; the current PCs all have 18s or 20s in their prime stats, after all. So... the wizard would get more mileage out of that 18, and the other PCs would get nothing (or another penalty).
But the point of the OP's idea is that such a rule would/should encourage the other PCs to maybe have 12s or 14s - that INT should be considered a "useful" stat for everyone. Like I don't care about having STR 8 on all my characters, except the heavy-armor-wearing paladin I played (and I still cheesed that one with mithril armor and STR 10!!)... but when I play Solasta (or BG3, a little), I make sure everyone has 10 or even 12 STR because there are frequent jumps you just 100% can't make without it, and it splits the party. (And in most CRPGs, STR determines carry capacity, and I always pick up everything.....)
So, yes, I'm onboard with increasing these under-valued stats, even if two of the 14? 20? classes will inadvertently AUTOMATICALLY get the maximum bonus from it too, because it will encourage the other 12? 18? classes to not dump the stat!
My idea for INT, btw, was not to straight give extra skills, but to give specializations or "knacks". Like every cleric has Religion, but your INT 12 cleric has a specialization in Undead, so when he makes any skill check that relates to Undead, he gets to add +1 to the check. You can give up two "knacks" for a specialization, and now the bonus is "+1d4" instead of +1. [I was also toying with related ideas. Like your first knack is random somehow, but the second could be chosen; why can't the rogue have the knack with Undead, while the cleric's knack is for Tumbling? Or having a knack with a specific weapon - "I've always had a knack with knives" - and getting that bonus to damage, or a once-per-fight accuracy boost?]
My house rule for CHA is "You get 1 free, loyal Contact for each point of CHA bonus." [You also get 1 or two for a detailed background, FYI.] You can define your Contact
DURING PLAY, writing them into the story as a resource or defining an existing NPC as your Contact (with GM permission). For example, upon reaching the County capital, the bard's player said "I'm going to go look up my friend Terranik. He owns a tavern here; he'll know what's going on, and I can get us all rooms for the knight." Poof, Terranik is now the owner of the Broken Shield tavern, lower west side. Later in the campaign, the rogue (a princess-type that sneaks out of the castle to go on adventures) decided that the guard on the East Gate of her father's city - where the PCs were trying to sneak into town after being banished (for reasons) - was an old friend of hers from childhood. A quiet conversation later, the guard was "tricked (wink wink) into chasing a sighted bandit", leaving the gate conveniently unguarded for a couple minutes for the PCs to slip through.
Does the bard have more Contacts than anyone else? Yes. And the Warlock does too. And it's okay; these charismatic PCs know more people, and it's fine. But the CHA 14 rogue enjoyed her moment at the gate, and now there's a better-defined PC-tied NPC in the world that she cares about. Win-win!
Sorry OP, WIS has enough reasons to keep high (Perception and save-or-suck saving throws)!