There are very few effects that couldn't be altered into a different element, yet alone a lot of elements.
Taking Dryspell as an example:
Deal 10 damage divided among all creatures. Gain
for each creature damaged this way.
Deal 2 damage to all creatures. Gain
for every creature killed this way.
Each creature loses 1 ATK. Gain
for every creature affected by this.
?
?
Wildfire
Deal 1 damage to every creature in play. Gain
for every creature damaged this way.
Lemons
Generate
for every creature in play.
?
Artimies becomes king of the world for 3 seconds.
Deal 1 damage to every creature in play. Gain 2 HP for every creature damaged this way.
?
So... Every effect can be cross-element, kinda.