I have traveled from KHI to ISB many times (offcourse with friends, not with Family ) on Mehran,Cultus, Accord (87 Model) and Vitz.
But all those travels were with friends and I can easily manage if something goes down. People living in punjab have no idea about roads of Sindh. Most of the times un roads py gari 50,60 ki speed py b nhe clala sakty, law and order ky b bohot masly hy. So unless you have not traveled on these roads I dont recommend to go for long drive in Sindh Area (Specially after Hyderabad).
Vitz is very good car and I have gone to Kashmir Nelum Vally and near Naran/Kaghan on my Vitz 1.0 Manual 2003, Vitz easily go there and on straight roads it reaches speed of 140, never tried to push more than that.
I think if you dont install stupid CNG kit in your car it will never betray you and you will enjoy your ride