First off, this isn't even a rough draft yet. It's a high-level WIP with a few details, and this thread is both to preserve ideas and let them be discussed/debated/improved on.
The halfling brew master is a semi-spellcaster whose special schtick is that the spell limits don't apply in the same way. Their magic is tied into the beers they brew. Anyone drinking them gains the effect, but they either sacrifice a spell slot of the same level (if a caster with an appropriate slot), or they suffer -X to all attack and proficiency rolls, where X is the spell level, and the penalty goes down by 1 per hour. Characters with Hardy People reduce the penalty by half to a minimum of 1. Each brew carried counts as an item, as they are in their own flask/skin/gourd/whatever. This means a high-level brew master is carrying a lot of weight around in magical beers.
Naturally, the brew master gets the equivalent of Dwarven Brewing at 1st level. Magical beer can be microbrewed as a single dose (one canteen, or 2 pints) or macrobrewed as a barrel (20 gallons or 80 doses). Brewing cost depends on how long the beer will stay good for. An unhopped ale, which will only stay good for 1d3 days, costs 50 gp per spell level per dose. Weak beer, which stays good for 1d6 months, costs 150 gp per spell level per dose, while strong beer stays good for 2d6+3 months and costs 250 gp per spell level per dose.
Much like a wizard, a brew master needs proper equipment to experiment with new spells. While major breweries may allow a master to experiment, a home brewer will need 2,000 gp of equipment to research 1st-level recipes, while each additional 1,000 gp will allow an additional level of recipes to be researched. As with a wizard, having 10,000 gp of extra capital investment will grant +1 to research throws. Unlike a wizard, a brew master may start researching at 1st level, but may never create permanent magical items. Any brew master research laboratory can be used to support Craft: Brewing.
Brew Master spell list:
1st level: Chameleon, Cure Light Wounds, Detect Magic, Detect Poison, Fellowship, Jump, Read Languages, Remove Fear, Resist Cold, Ventriloquism
2nd level: Augury, Bless, Cure Moderate Wounds, Detect Invisible, Detect Secret Doors, ESP, Inaduibility, Invisibility, Ogre Power, Resist Fire, Speak with Animals
3rd level: Clairaudience, Clairvoyance, Cure Blindness, Cure Disease, Cure Major Wounds, Fly, Gaseous Form, Growth, Haste, Infravision, Water Breathing
4th level: Cure Serious Wounds, Dimension Door, Dispel Magic, Divination, Find Treasure, Giant Strength, Neutralize Poison, Polymorph Self, Protection from Evil (Sustained), Tongues, Vigor
5th level: Contact Other Plane, Cure Critical Wounds, Dispel Evil, Restore Life and Limb, Scry, Strength of Mind, Teleport, True Seeing
All of this is subject to change. I tried to stick to spells that only affect the caster so that it would make sense that others could drink the brews. I haven't looked at hit dice (probably d6) or combat (probably 1a with a downgrade of armor to Broad and weapon categories iii and vi). Since they have pretty strong limitations on their spells, and a list of 11 spells per level at 1-4 and 8 spells at 5, I'm OK with declaring this a pseudo-Divine class and giving it full Cleric caster equivalence (so HD 1, Combat 1a, Divine 2). For a code of conduct, the brew master never intentionally skips a meal, will not chip the glasses or crack the plates (or otherwise damage tableware), and will do anything within the limits of their alignment to sample a brew they've never had before. The lack of spells at 1st level gives them a level to gain treasure before having to spend it on the magical brews they make. Note that unlike normal divine casters, brew masters do need to find (or research) recipes for their magical beers.
The focus on curative and cognitive spells could lead to some interesting trade caravans - maybe those merchants are hauling a wagon with a couple kegs of Cure Disease beer into a plague-ridden village? Or what happens when a group of halfling bounders are given flasks with Ogre Power to use when bandits approach? Sure, they'll suffer -1 to hit for drunkeness, but they're still at +2 overall.
And, if you're a halfling-hating misanthrope, this can be re-skinned as an Elvish Vintner, making fine wines and cordials instead of beers.