Trading spells for BAB

[Rub-Eta]

My idea for a new house rule is to allow players (and DMs, of course) to trade down in spell progression in order to up BAB progression.
Ex:
An Arcanist can be converted to a 3/4 BAB class with 6th level casting.
A Magus can be converted to a full BAB class with 4th level casting.

This could become a problem with Clerics, since they'd become full BAB with 6th level casting.
Anything else I should consider before attempting to implement this? Should the trade be more compensated than just BAB?

[The Dandy Lion]

The cleric may actually be alright, as it is utterly devoid of class features. It still gets bonus domain slots, however, and that would probably push it over.

Shamans and Druids would be crazy good in comparison. Druids get Full BAB with Shillelagh and Wild Shape as well as a pet and great control spells.

My girlfriend discussed a similar concept with me - reducing 9-level casters to 6-level casting in order to allow them in a format that would otherwise ban them. In general, I see a couple of trends you need to adjust for.

6-level casters have a ton of class features. Often temporary ability enhancements to bring them to martial strength for a limited period. We're looking at Bardsong, Bane/Judgement, Arcane Pool, Fervor, Studied Combat, Mutagen, and Legacy Weapon are all examples of this - they're above the power curve for spells, typically due to action economy.

Otherwise, we have this kind of problem. You can't invest too high in a casting stat, otherwise you'll have a small number of spells per day and a very mediocre fighting ability.

Invest in physical stats, and, well, why are we playing a wizard over a magus? The Magus has several magnitudes better action economy, and heck it even has better staying power thanks to arcane pool and spell recall. You're about as good as the caster Vigilante archetypes thanks to the school, but those kinda highlight why 3/4 bab + 6-level casting doesn't keep up without some extra oomph.

On the 6-casting to 4-casting situation, that is a lot more complicated and I am not sure how to approach it. On the better side of comparisons, you're comparing the 4-caster Bard with an Oath of the Peoples' Council Paladin. On the worse side, you're comparing a Magus who cannot use half of his class features to a Bloodrager. I think I would sooner stick to Archetypes like Kensai, Arrowsong Minstrel and Molthuni Arsenal Chaplain in those kinds of situation.

[My Self]

This is only a good trade for divine fullcasters. The Shaman, Druid, Cleric, and Oracle can go to full BAB 2/3 casting, which is a very potent combination. Bards, Inquisitors, Investigators, and Mediums can get by with less casting, although most of them will be gimped compared to their regular versions. Arcane and Psychic fullcasters never win in the trade. Most 3/4 BAB 2/3 casters have action economy boosters and pseudo-BAB boosters. Divine fullcasters don't have action economy buffs, but most have excellent self-buff spells which push them far above and beyond full BAB equivalent. It's a little like the Warpriest, but with better base BAB and worse action economy. The Cleric archetype which drops a domain for Bardic Performance ranks a bit higher, since you basically become a Bard++, with full BAB, 2/3 casting, and an extra hit/damage boost. Oracles and Druids, on the other hand, win completely in the trade. Full BAB full Wildshape is comparable to Rage and all the other Rage powers, never mind the 2/3 casting, optional Animal Companion, and all the other assorted features you get. Oracles have good class features as well, and taking battle oracle type abilities will make you competitive or better than regular martials.

[Cyrad]

3/4 BAB, 6-level spellcasters generally get more or stronger class features in order to help them scale. Some classes like the magus also get abilities to help them be competent at combat. Those classes can easily become stronger than other martials if you make them full BAB classes.

So simply shifting them will result poorly balanced classes. Classes are designed with their BAB and spellcasting progression in mind. Screwing around with it will cause some major problems.

[Rub-Eta]

Thanks for the pointers so far!
I know that balance is a large issue here, but I'm not too interested in that at the moment. It will be an option, nothing to be enforced in anyway. The only balance I'm really concerned about is if something actually would end up stronger this way - I'll take a look at the divine full casters.

@The Dandy Lion: Good catch about the Magus. I didn't even think about that. Too bad.

@Cyrad: I don't know about that - no 6th level caster has anything to actually match Rage or Smite. I don't think they'll climb higher.

I'll probably end up not passing this as a general rule and only allow it for "safe" classes. I'm mostly interested in the Arcanist (Wizard+Sorcerer), Bard (+Skald) and Witch, where I don't really see a big problem.

[Vatras]

BAB is the most craved thing in Pathfinder when you look at builds and what players try to make. It follows therefore that it is the most powerful or useful thing to have in the game, else there would not be that intense interest.

And in conmsequence of this I would never allow anyone to acquire it outside the ruleframe, i.e. by multiclassing and paying the price in class features and progression.

[Rub-Eta]

What? You are aware that the classes who are considered the strongest are those with full casting, right? BAB doesn't really come in to it.

[My Self]

Rub-Eta wrote:

What? You are aware that the classes who are considered the strongest are those with full casting, right? BAB doesn't really come in to it.

Vats said that BAB is the most craved thing for builds, though I'd disagree that it's the most powerful thing in the game. It's just that full casters don't need to build to be effective.