Well Vader is certainly a very powerful character, and while he is not nearly as fast as before the prosthesis, he is still pretty quick with the force and can act pretty fast when he enters a combat situation.
Just check his encounter with the fastest gun in the galaxy: Han, despite shooting first, has his blast shot stopped dead by Vaders bare robotic hand.
This is a very canonical example of Vader displaying a Foresight-like attack deflection.
THe "on protection depletion" feature could perfectly be replaced with your dark lord's power.
The +1 speed per negative effect applied would be a permanent speed increase which would make him more dangerous as the battle rages on, making him more dangerous over time, which is fitting to the awesomeness of his character.
