In my opinion what should happen is this: Spells should be calibrated to the Hasty Action Rules under Haste B346. Spells taking HALF the time is a -5 Feat, which means it requires a skill of 20 to have a >95% certainty or looking at it in another way, a spellcaster with skill 15, can performing this amazing feat at the cost of 45% certainty!
On the other Hand, when you look at the Skill-9 entry you already have 1/3 chance of success and the casting time and cost are double! Isn't the risk punishment or deferent enough. If you multiply the risk and the additional gains for high skill you have a very steep rising curve of economic profit for the action. My Opinion is to make it a more reasonable Climb.
In my opinion, what should happen is that at Skill-9 where the Spellcaster multiplies the time to of the action by 32 to have a 90% certainty of success basically makes a spell like Ignite fire take 32 to seconds or half a minute, a 2d Fireball a whole minute.
Nerfing Magic in upcomming Fantasy Game.
x6 all Casting Time. Since the default is 1 second, at 6 seconds a 3d fireball will take 18 second. Hasty casting will be a feat of -9 will bring it down to 2 seconds. Extra-Time casting of x32 will take 10 minutes! Analyze magic will take 6 hours!
Low Magic. Basic part of Nerfing magic. A general -5.
Rolling For Spells. There should be some random element in spell access. some, the most basic ones are very easy to access.
Infrastructural and Economic Consequences. 2% of the modern population in a developed country is in food production. Thats how effective and efficient technology has become. It allows these 2% to make 150x more food and all other specialties and export. An economy that can support a BIG chunk of its GDP in security or army. In economics, Armies are not like Businesses which grow to meet the demands and quality of life of its population. Armies and Espionage is the price we pay for a quality of life that we can never figure out how to cut. Even if spells that peer into the future affecting the Information Asymetry, all the progress Magic may be providing may just be all drained by the armies, spies, diviners, monsters and special equipment and investments made in defense of each land.
The trick of finding Equilibrium is enforcing an appropriate cost to the Magical Action. I will draw on a historical era and just look at how many engineers, architects, scientists, managers, builders and planners to keep civilization running and convert all those peoples to mages. Cost of their education and skill, the same as that of an engineer or scientist... as well as the gravity they are capable of given time and resources.
Basically what I could do is tak 15C economic data and converting to swords and sorcery.