I think this would be a great addition to the thief spec. When you think of thieves what do you think of? You think of shady individuals in a market where as soon as the owner of a stall looks away the thief strikes. The owner then turns his head and to his dismay something of value is missing. He then looks around in a shock to see a man quickly fleeing, to be able to get away, he would need this kind of agility.
If the thief pickpockets someone and is caught, do you think he would just run away? No, what he stole is where he gets his livelihood. He would jump, leap, slide, climb, and anything else he could think of to get away. This is why I think the ability to do all the things portrayed in this mod would be useful. It brings more realism and action to the difficult life of a thief.
On the other hand of things, the actions portrayed in this couldn't realistically change the way a thief fights. Simply put, this is for running away and fleeing, something only a thief could use to its advantage. The thief realistically is only formidable with a sword, even if it has a bow, the bow only does around 7 damage a second if you were hit with it. This is why I couldn't see these actions being useful in any way in pvp, it simply are only for escaping, not fighting.
The thief does not have many skills just for itself, most of its skills are taken from other specs/classes or simply do not work. Incorporating something like this into thief could give it its own skill that could only be useful for a thief. Also because of the ever approaching jump to max level of 60 for specs, there could definitely and easily be space for it in the list of a thief's skills. This mod would be a working, productive, and useful addition to a thief.
I hope you really consider this, it could be a very great addition to thief, thank you for reading.