Unless there is no other way than walk through a surface covered in fire, ooze or poison, the characters will always find the shortest safe way around.
That itself also poses problems because VERY often the path through the fire is the FAR better choice (In fact a lot more often than you think).
Even then the safe path might be some ridiculously long path that takes up your entire turn.
It would be better if you could SOMEHOW plan out your move
