Impact of allowing characters to change their main casting stat

Question

I have never really understood the rationale of "wizards use Int, clerics use Wis and sorcerers use Cha". So for my new campaign, I am considering getting rid of that rule, and allowing characters to change their casting stat, for example allowing a cleric to swap Wis with Int, or a Wizard to swap Int for Cha.

Obviously, it would be a swap, so all features would exchange. For example, a Cleric swapping Cha and Wis would use Cha for his casting and Wis for his Channel Energy. This would work only for mental stats. And finally, this would apply only to class features

My question is: How would this affect the game?

I am mainly looking for balance issues that I could have overlooked. Bonus credit if you can arrange them as Critical Issues, Major Issues, and Minor Issues. And even though insight for 3.5 can be useful, this is for a totally 100% Pathfinder game.

Update:

There were a lot of good answers touching on different points, so I figured I would sum it up a bit here:

• Intelligence might be chosen by everyone, as it gives a better advantage (skill points) than the others (bonus on Will saves for Wisdom, bonus on social skills and spell-like stuff for Charisma).
• Class skill lists might need to be changed.
• It can make some multiclassing concepts more powerful by reducing MAD

Answer 1

The main issue is the difference in how useful Int, Wis, & Cha are for non-casting purposes.

Intelligence: great for everybody, since it gives more skills (plus it boosts knowledge skills, which tend to be popular with casters)

Wisdom: meh; it boosts your will save, which is nice, but most casters have pretty good will saves from their class anyway, so an extra 2 or 3 from wisdom isn't a huge issue; it also boosts listen/spot (the thief/ranger's job) and sense motive, which the cleric might care about

Charisma: dump it; all it offers is a small boost to social skills (which aren't class skills for most casters) and a small boost to your leadership score if you take the appropriate feat

Thus, any optimization-minded character will probably convert to Intelligence-primary.

Some feats & prestige classes may have ability score requirements; you'll have to decide whether you want to swap those requirements as well for characters that swap.

The other thing to watch out for is that this reduces or even eliminates the MAD (multiple attribute dependency) problem for characters that multi-class between two caster classes. Multi-classing is a pretty poor choice for casters to begin with (from an optimization standpoint), so this isn't a huge issue, but it's something to keep in mind.

Answer 2

Pathfinder vs. D&D 3.5

There really aren’t any major differences between the two as far as this is concerned; the only one is for non-Core spellcasting classes (Beguiler, Spirit Shaman, Wu Jen, etc. for 3.5, Witch, Magus, Oracle, etc. for Pathfinder). I don’t know enough of Pathfinder to know if any of those non-Core classes is going to cause significant unusual problems that the Core classes would not cause. But for the Core classes, nothing much has changed.

Critical Issues

None, really. It’s a pretty minor change, really.

Major Issues

Not all ability scores are created equal. For example, Intelligence gives skill points, Wisdom gives Will and Perception, while Charisma gives just social skills. Don’t care about social skills? You probably don’t care about Charisma.

But, that’s fairly minor, considering that the Charisma-based class here is Sorcerer, which is a fair bit weaker than Cleric, Druid, and Wizard. By swapping e.g. Channel Energy when you swap Cleric spellcasting, you avoid the other potential major issue.

Minor Issues

Feats and prestige classes will have to be swapped (or not) on an individual basis to match any swapping that does occur. This shouldn’t be hard, but it will be a thing.

The last bit is that skill lists might be awkward. Pathfinder is a lot better here than 3.5 thanks to the better rules for cross-class skills, but basically the issue is that class skills generally favor the ability score that a caster uses for its spells. Wizards get Knowledge skills, Sorcerers get Bluff, etc. It might be nice to allow the characters to change around some of their class skills when they make this swap.

Answer 3

@KRyan touched on most of the points I'd have mentioned, although I'd like to add one:

Creating ability-score synergistic characters is one of the basic ways players have to create more powerful characters. Adding no-cost key ability score swapping for spellcaster is likely to significantly increase the number of ways such characters can be created.

In other words, you're going to be dealing with new optimized builds, some of which may outstrip the effectiveness of pre-existing options.

Ironically, considering that Charisma is usually considered the least generally useful of the three mental stats, I'd be most worried about switching spellcasters' key ability modifier to Charisma, on the grounds that Charisma can be added to a great many things, and is thus rather easier to build around than the other stats.

Answer 4

I have never really understood the rationale of "wizards use Int, clerics use Wis and sorcerers use Cha".

Well, if you go all of the way back to D&D 2.0 or AD&D, the "sorceror" class did not exist at all. So Charisma was originally never a casting stat at all. This made a Cha a dubious stat for min/maxers, especially before the advent of "Use Magic Device" as a skill.

As it stands, PF really has a flavor where Int = learned spells, Wis = divine spells, Cha = innately cast spells. Most of the classes abilities are balanced around that.

On the balance front.

Major Issue: skills vs. class archetypes

For example, Wizards typically have lots of skills, particularly knowledge skills, this is kind of a Wizard "thing". Clerics generally have a limited number of skills unless they contribute a bunch of points to Int instead of Cha (skills vs. channeling). That "skills limit" is definitely a Cleric weakness. If I can make an "Int Cleric", I can suddenly double down on the skill points and still get good Cha for channeling. The "Heal" skill is still wisdom-based, but the "Int Cleric" will likely make up for that in extra points and end up ahead.

You will see the same thing with the Bard class. Skill points for Bard are 6+Int, but Cha is the casting stat, so their Int is probably limited. If a Bard becomes an Int caster, they get an explosion of skills. You'll find a similar thing with Paladins and Rangers.

Minor Issue: Feat Requirements

If you change the "channeling stat" are you equipped to handle changing all of the "channeling feats"?

There are multiple feats that have stat prerequisites that are tied to class abilities. If you switch casting stats are you ready to switch up those feats all of the way down?

Answer 5

Swapping mental stats seems reasonable to me. I've always wanted to play a more intelligent cleric. I'd worry about casters with physical stats though. My first thought was to player a caster with max constitution to avoid glass cannon syndrome. I'd also worry about any sort of sword-mage/gish build that could suddenly afford max strength.