cantilever

Please refer the typical floor plan suggested by my architect.

my architect has suggested a 30 feet length corridor on 8 feet cantilever beams, to hold the corridor and two rows of stairs each 4 feet wide. is this design ok or is it risky or extreme kind of design since i have seen cantilevers are generally not used beyong 5 feet generally. do you suggest any special care? 

further, can you suggest any optimization of the plan w.r.to location of toilets, lift etc. 

Also, one pillar was not placed at lift location to keep the pillars to even number. but is this safe enough, particularly in light of the cantilever.

Thanks.

Kalyan