As good of an idea this sounds, it doesn't really make sense balance wise. The ranger's get the use of a bow and arrows, which means from said cliff they can attack from a range, it would be unfair to give them another advantage on top of ranged attacks. Not to mention rangers get full chainmail which can absorb fall damage, and the track ability.
For ninjas, it may be a good idea, but a level 50 ninja gets smoke, which renders the ninja invisible for 10 seconds, perfect for sneaking up on unsuspecting adventurers. However, the ninja is fairly similar to the theif in abilities, and it does seem likely that a ninja would be able to safefall, if you watch any old school kung fu movies you'll notice that ninjas jump around as if lighter than air. Which brings me to another spell for the ninja, which is jump, it seems only logical for a ninja to have. Ninja's happen to be the only rogue spec without 5 skills if i remember correctly. And if dragoons complain about ninja's having jump, just realize how OP dragoons are because they can wear armor as well as jump around or charge at proving extremely difficult to kill vs any class that doesnt have more armor, and health.
Anyways, giving something to ninja's seems like a fair opinion to me, but not so much to rangers, they already have a pretty nice skill set.
