While I understand what you are saying with that... why would we want to limit the spells by taking away from the creativity of writers?
I remember years ago... D&D and trying to tell my wife at the time that she could not drown someone by creating water in his mouth... the rules say you must have a container... But as the rules here are being developed...why would we want to limit the fun of new ideas?
If someone wants to TRY and cast the examples you stated... I see no valid reason to stop them. Protect water could indeed protect the water of a sacred basin so that no one may poison it.
If an elemental best of fire is after you... you must harm the fire, using water or what ever your fun idea may be.... but you must harm it right?
Open minded thinking is where the fun comes in... guided by the limits set in the game... but designed to be a fun story. Lets not restrict it too much with rules designed only to restrict.
