Is there any way in which I could make an object move by impulse, and not by the default translation the nav mesh agent does?
Only if you move it yourself. You can get an array of positions back from navmesh and use that, but move it yourself.
how should I go about that? set the speed to 0 and then just do as you say, move it according to the data i get?
Well you'd be in charge of the entire movement - ie a character controller or physical object. You'd just be using navmesh to generate a set of points you can use however you like...