Cantrip damage like acid shouldn't cause -2AC if it's not in the rulebook; Fire Bolt should not leave a fiery area with nothing to set on fire, Ray of Frost should only freeze the ground when there's liquid on it, etc. -- maybe rein in surface effects in general (debate)
I prefer the surface system for what it's worth. Right now they have some utility for setting up chain reactions with a well placed web or barrel, while with the Rules As Written (RAW) it's pretty much 'pick damage type' for a ranged attack.
I would counter by looking at the source game, and how it has been balanced. Virtually all spells that leave lingering damage are Concentration.
Speaking of Concentration:
-Remove ground effects from Cantrips OR allow us to choose between the ground effect or the attack roll -If a ground effect is created, it needs a SAVING THROW to completely avoid it. -Currently, Concentration is incredibly difficult, a single firebolt can provoke up to FOUR concentration saving throws while concentrating on a spell. This is a CANTRIP. Running across a burning floor can produce MANY saving throws. -Moving across surfaces: In 5th edition, almost without exception, you take damage if you END YOUR TURN in a hazard, meaning that if you can scramble out of it with your movement, you take no damage. I don't think most of us would care that much about the cantrip surfaces if this was the case