More summoner spells should get the smite treatment
IE: Items you can get and/or enchantments you can get that will slightly alter what your spell will do.
Imagine if
could get an enchantment that gives you extra tenacity or the next basic attack vs. a champion turns into a leaping strike
Imagine if
could be used on the entire team or the shield is a spiked shield, dealing damage equal to however much is taken away.
These are just super simplistic ideas but I can't help but feel that the idea behind giving smite more utility could be a wonderful step in diversifying the summoner spell pool.