If you start giving SCH access to AOE Haste/CritHit+/MaB/Acc/Eva/This/That/TheOtherThing... all you're doing is creating a new breed of BRD or COR and cutting down the strength of SCH by giving him too much to do; Like a RDM--Jack of all trades, Master of none.
As far as Divine Magic goes... don't really care. The Banish line of spells are limited as it is and Holy is a "Holy Waste of MP". Flash would be a nice spell, but then again, you're stepping on toes that don't need to be stepped on.
Since the release of afflatus for WHMs, holy has actually become a worthwhile spell occasionally. I personally would cringe at using flash on my SCH, simply because SCH is such a hate factory already. Flash would only really be useful for soloing and needing an emergency stoneskin recast. Flash > celerity > stoneskin would be 100% chance of getting it off on any mob that isn't in hundred fists mode. Celerity > stoneskin usually does the trick anyway, however. Banish's main quality is the defense down effect and the fact that it removes all penalties from weapon damage types vs undead mobs. Because of this, Banish 1-3 would indeed be welcome for certain situations, but nothing to grovel to SE about.
On the other hand, I personally would love to see a small boost to stormsurge. My ideas are as follows:
Firestorm: STR + 3, attack + 3%. Each additional level: STR + 1, Attack + 1%
Rainstorm: MND + 3, Macc + 3%. Each additional level: MND + 1, Macc + 1%
Thunderstorm: DEX + 3, Acc + 3%. Each additional level: DEX + 1, Acc + 1%
Windstorm: AGI + 3, Eva + 3%. Each additional level: AGI + 1, Acc + 1%
Hailstorm: INT + 3, MAB + 3. Each additional level: INT + 1, MAB + 1
Sandstorm: VIT + 3, Defense + 3%. Each additional level: VIT + 1, Defense + 1%
Aurorastorm: CHR + 3, hHP + 5. Each additional level: CHR + 1, hHP + 2
Voidstorm: All stats + 1.5, hMP + 5 Each additional level: All Stats + .5, hMP + 2
None of this would be game-breaking by any means, but would very well have its place. All of these bonuses can be comparable to the corresponding COR rolls when COR is the subjob, there is no corresponding job, and you roll a 1-2 on it.