By ‘cantilevered staircase’ I presume that you mean one where the treads cantilever sideways from a wall to one side, with the other side open, which can look fantastic if the design detail is done with great care. One of the big issues here is that each tread is a long platform supported at one end – a bit like a diving board. Clearly, if the tread is going to be able to carry the weight of a person at the open end, the leverage that this weight will apply to the tread is very significant so it all relies upon how firmly the tread is anchored into the wall (and that the wall can take it). The firmest junction is created by making the treads over-long and built deeply into the thickness of the wall (ensuring that the wall is thick enough to do so).
From all of this, you can see that it is vital to give detailed consideration of the design and support of the staircase at a very early stage of the design process so that the wall, its support, construction and thickness are all suitable for the task of carrying the stairs. It will be important to get the staircase properly designed and drawn up and your designer will need to work with a structural engineer, who will do calculations to ensure that it will be strong enough. Please note that if you are intending to support the balustrade and handrail on the open end of the treads, it’ll make the lever effect more significant.