I have heard Deba sing and I so badly want her to sing in the show herself, she is an awesome singer.
But, imagine this - Shaurya starts singing some song (guessing the theme and all, they might keep it to some punjabi mixed folk song type) then suddenly, Ahir starts singing the parts and it becomes more like jugalbandi. How cool would it be and that could get Shaurya really mad when Anokhi praises Ahir for excellent singing.
As comedian Kapil sharma says, almost all punjabi folks (more than normal ratio) are very good singers.
I adore Hitesh - I wish someone gives him a lead role, he would be so cute as the romantic male lead.