Personaly i dont think theres any harm in buying sucha car. mayb the price wud be lil leser then market, depending on the condition of the car. (if its in ruff condtion obviusly it wud go for less, if its in excellent condition it shud go for market value or the amount ure wiling to pay)
and consequences, no if ure going thru a legal process. These days when u transfer an old car on your name (driving a car with open letter is trouble at all times nd kinda bewaqoofi too), you get a new registration book. So if u have all the legalities theres no issue in case any body stops you at any check post or provincial borders u can call the karachi CPLC nd prove that youre right and the documents also prove that ure the owner so theres no as such issue. secondly your new registration book with official stamps is proof enough for anybody bothering you. 
PS : Hope it help,
and stolen cars arent some thing that u shud avoid them, no body wants to get there cars stolen, S**t happens. so that doesnt mean u shud keep ur hands off it. or buy it at the price of garbage
