Saving throws
These may need to be adjusted, depending on how hard it is for characters to make their saves with the new spell rank system.
Static Defenses
Static defenses - As in 4E, setting up some way for replacing saving throws by instead setting the DC of the roll for the spellcaster using something like "target has a 15 will save, roll spell attack vs DC 15 to see if you hit them". This would also make it possible to roll only one time for an area of effect, rather than one for each affected creature. There is a risk that this could cause a single good roll by an enemy spellcaster to wipe out the group. As such, it may be necessary to eliminate "save or die" type of effects. It may also be necessary to set up multiple levels of fail (e.g. fail by more than 5, target takes no damage, or succeed by less than 5, target takes only half damage). Damage levels may also need to be adjusted (in favor of more spells that are less powerful).
Spell Resistance
Changing spell resistance could also simplify a lot of rolls. You chould change spell resistance to instead only offer a bonus of +x on all saves vs spells (and spell like effects). That makes it operate much more like a "resistance bonus" instead of a "miss chance" (as it operates now). If needed, you could also allow a save of 0 + SR for spells which normally allow SR but not saving throws (so that it was possible, but not likely, to save against those effects). The granted bonus should be somewhere in the range of old spell resistance divided by 10 (or maybe 8). Care should also be taken to adjust the amount depending on the roll required (bonuses act very differently in 3d6 vs 1d20). It has also been suggested that SR automatically grants a creature Evasion as well (take no damage on save, if normal was to take 1/2).