I'm more worried about people spamming "light" and "create water". The latter completely eliminates deserts while the former could be used to create a large number of light sources and annoy people. Maybe a line about how you can only sustain one copy of the level 0 spell at a time, so when you cast light, any previous casting is automatically dispelled? Doesn't do much for Create Water since that's instantaneous, but it's the spirit of the thing.
Hmm...Probably the best Solution for create water is either a)put a limit on the amount of water you can produce over a certain amount of time or b)require it to come from a natural source.
b opens another pandora's box(think Boogie Power's effects on Alibaster) but it would also functionally work.
I don't see light being a problem since all darkness spells are of a higher level than a 0 level spell. Create Water can be a problem. It would bring back the 2nd ed. ability to create it in your opponent's lungs except the room this time is filling up and all the opponent's need to swim or die.
I think in the end, with the amount of time it takes to fill said room with the current room...unless there are garuntees that the dude won't escape(or break something down to release the water) I don't see it as a problem...and if there are, I would say let them with the amount of work it took to do it.
Although...why do that anyway, when there is another spell that if properly bound, can grant them a slow and painful death(infict minor wounds)