maybe a masterful alchemical (sp?) potion gives the desired effects, while an average one does nothing. potions with no quality give opposite and adverse effects.
Exploit: order your beginning alchemist to produce potions of weakness. Another one: potion of intelligence. drink. make another potion of intelligence, but better because you're smarter. etc. (cfr. TES:Morrowind:).
The recipes don't need to be completely random, I agree. You should be able to stockpile specific ingredients to prepare for certain.. situations. What I'm trying to avoid is nameless alchemists in cubicles, mass producing game-breaking potions. How?
- Alchemists should tend to live in a sphere-appropriate way (materials, furniture, environs) for the stuff they make. They'll demand or buy appropriate stuff and pick appropriate living quarters if you let them.
- Attuning a potion to a specific person, time or place. In most cases that might be limited to adding an ingredient or changing a procedure (eg. shaking instead of stirring), which the alchemist does automatically. Special procedures (preparing it at a mountaintop, submerge it in a well, etc.) might be added also - they could be part of some regular recipes as well.
Without additional effort like the above, potions shouldn't be more powerful than a cup of coffee or a mug of beer. The effect will be that your alchemists need a dazzling variety of ingredients, something that the game is very well suited for. They'll also develop recognizable living quarters and clothing.