If you have the ability to jump on top of boulders you normally wouldn't have had access to, which means the mobs probably aren't able to get up there too, doesn't that kinda make the ability.....overpowered, at least I think that's the word I'm looking for. Just my opinion though.
The built in god mode is overpowered as is the Bag of Holding mod in Oblivion. But, to be honest, that's not really the point. Some folks just like to mess around, some like to role play, and so on. It's not really an issue. Being overpowered is something the player decides for themselves and some may still enjoy it even if something is overpowered.
Anyways, on topic, something like this should be fairly simple to implement if there's something like a gravity strength variable or jump power or something that is specific to the player or something similar to that.