how would the various super Mario bros. abilities/suits work as ars magica spells?
Most of them are already there.
Jumping: ReCo 15 - Gift of the Frog's Legs
Super Mario: MuCo 15 - Preternatural Growth and Shrinking
Fire Mario: CrIg 35 - Ball of Abysmal Flame (or just Pilum of Fire (CrIg 20) if that's sufficient for you)
Breaking Blocks: PeTe 10 - Fist of Shattering
Breathing Underwater: MuAq(Au) 20 - Lungs of the Fish
... sticking to the old SMB here. Covering all the later games would mean quite a longer list. 
how about form of man-frog(MutoCorpus(animal) for the frog suit?
not sure how to make that spell, if you have ANY ideas feel free to put them on this thread.