So I'm thinking of adapting the 4e spell mechanics regarding force to 3e and I figured I would ask y'all what problems will I have doing it. I plan to still use 3e spells but add cast at whatever force you want. What should the nuyen/karma cost be for these spells? what spells are going to become too powerful? Thanks

I also plan on using 4e style specializations but I don't foresee that causing any issues.

Suprised no one posted on this. Any combat spell, most illusion spells, and some manipulation spells, like shape element or some extended range spells. Force is far more important in SR3 and every magicain starts with a base of magic six. Do you want a force 12 deadly anything?

The cost and availibily also goes haywire. It is doable but you will need to address the availibily, cost and karma issues.

Setting a karma of 8 or 10 per spell and a force 8 multiplied by max damage code would be my start point. Harsh but you just made spells crazy powerful. People are going to go spells at creation greedy with these rules though.