After reading
this rant on magic I cooked up some of my own ideas about how magic could work in DF.
I agree with Cpt. Failmore. It's the schlubs and practical people who make DF work, and in some ways, fun. You don't want to overshadow them (and the tons of soldiers you lose) by micromanaging a wizard so he can unleash teh perfect fireball. Magic gives you diminishing returns on fun the more effective it is.
I would like to see magic, just more as he described. Wizards being more about random "fun" than benefit. More chaos is usually more fun, and I think magic would be most entertaining if a dwarf wizard were like the noble from hell. If wizards were just combat oriented, like soldiers with area-affect attacks, they wouldn't be as much fun to have.
I could see their default job as "ruminating" where they wander the fortress away from crowds and think. Personality would play a large part in a wizard's behavior, especially "Openness to new ideas and experiences, quick to anger, confidence and cautiousness" When they decide what they're going to try, you'd get "Soandso McWizardry goes to work."
And then they....
make it rain indoors
turn dwarves that piss them off into toads permanently
raise the dead inside the fortress
create a golem that enjoys walking through walls and doors (and who occasionally fights)
summon familiars that tend to poop everywhere and create miasma, and eat enough for three dwarves
randomly set things on fire
create permanent chasms in awkward places while screwing with the fabric of space and time
roll back (or forward) the seasons
summon demons/magma men/elementals
cripple your peasants by making them take part in "experiments"
experiment with captive animals/creatures, creating "super Goblins" or "super elephants" that then breed
make your plump helmets come to life to become mushroom men that attack your farmers
change people's gender (which either requires some same-sex coding...or it would end a marriage and give both dwarves MASSIVE unhappy thoughts)
mind control people (automatically making them friends, or old friends, possibly usurping elections)
polymorph random things (changing furniture into say, a rock, or a kitten into a tame Giant Olm)
change
wood into SNAKES
wood to stone
flesh to stone
stone to flesh (This Flesh Throne menaces with spikes of flesh and is encrusted with globs of flesh and encircled by bands of flesh)
mind wipe people (wipe their personality traits, making blank slates effectively)
create an epically huge stinking (miasma) cloud
teleports someone or something to a randomly location, possibly straight into HFS
tests an area of affect slow spell by casting it on themselves and then walking around your fort
...in other words, cause trouble.
Occasionally they might do something useful like....
throw a moderate fireball in a combat situation
enchant something (basically a high value decoration, like a singing instrument or talking sword)
move an impossibly heavy object or several objects at once with levitation
create food
instantly construct something with magic (at a variable quality)
produce an artifact (basically a strange mood...except wizards demand very high quality materials and aren't limited to one artifact in their life time)
duplicate a non-artifact item
...which we will call "spell casting."
But in general they would be a pain in the ass and trouble for your fortress.
They'd also run a higher risk of MADNESS than other dwarves. Their work regularly exposes them to good and bad thoughts of high magnitude...
"Soandso McWizardry pondered the infinite and was terrified/amazed recently"
"Soandso McWizardry had a failed/successful experiment recently"
An Insane Wizard would cause trouble at random on themselves frequently, so they would take themselves out of the picture quickly....(imagine a mind-wiped wizard wandering your halls) but not before doing some damage. A berzerk wizard would go full combat spells and throw lightning and fireballs. Wizards don't get melancholy, they go out with a bang one way or another.
The ways they show up could be varied. As was suggested in that rant, they could be homegrown, and the compulsion to become a wizard could be like a strange mood (and also based on personality, probably "enjoys intellectual discussions".) They might need an alchemist's craftshop or a new kind of workshop (library?) to take over, and require some kind of material to create their spellbook. (Say, leather, dye, cloth and bone?) Or they might show up on their own, or as part of the King's retinue. You'd probably want a character like this late in game, when they can't permanently cripple your fortress with their prestidigitation.
When they're not ruminating, spellcasting, causing trouble or doing default jobs, they're researching. Researching, in addition to other magical activities, is what gains the wizard job experience. Higher ranks of wizardry give the dwarf more options for what to do when they've finally settled on something. Researching would again require a craftshop for the wizard to work in.
I know a lot of people aren't sold on the idea of magic in DF, but cmon, how awesome would all that be, and what kind of stories would it produce?