Let's start with the base class. I think the Bene Gesserit is closest to the Cleric so we'll start there. This means we've already covered all the XP, Hit Points, Saving throw and so on, and don't need to restate any of that.
Now there are some differences from a Cleric and we'll do that by changing the spell list a bit.
- Replace 'Light' with 'Charm Person', duration: concentration -- This is 'The Voice'
- Cure Light Wounds (et al), this are all personal only -- This is 'Prana-Bindu training' and 'Internal organic-chemical control'
- Detect Evil, with the 1 hour duration replaced with 6 x 1 turn durations per "casting" per day. -- This is the 'Truthsayer' ability
- Purify Food and Drink, instead of working for 12 people it's personal but with 12 uses per "casting" per day. -- More 'Internal organic-chemical control'
- Unarmed attacks do d6 damage -- This is 'Prana-bindu training and the weirding way'
We want to encourage them to disdain armor so we'll also include:
- Unarmored AC Adjustment: +3 -- More Prana-bindu and weirding way
We restrict the class to Women, and everything else we can use "as is". Even turning the undead - we can say they're using 'The Voice' against the undead.
Comparing this to our previous version of the Bene Gesserit the new philosophy gives us something much more streamlined, and usable:
Bene Gesserit Sisterhood
Unarmed Attacks: d6 damage
Unarmored AC Adjustment: +3 [-3]
Changes to Cleric Spell List
Replace 'Light' with 'Charm Person' with duration: concentration
Cure Light Wounds (et al) only affect the caster
Detect Evil 1 turn duration but can be used 6 times
Purify Food and Drink only affects the caster but can be used 12 times
Gom Jabbar - No Damage, Save vs Poison
Edit: Forgot to add in the detail about Charm Person's duration!