Vitz is good ,economical ,powerful(1300 cc is powerfull,1000cc is not that good) but maintanance cost is expensive and if u run the car on cng it might have some problems as the vitz have CVT tranny which is not suitable for cng.PLats is a vitz with a trunk it has the same pros but one extra con is Low Resale Value
Cultus is a good car but it is a suzuki and the built quality of Pak suzuki is crap.cultus is not that powerful and it is not at all comfortable if compared to all the other options u have.
the best option is civic 96-98,its powerful,its comfortable,its economical(as i m getting 13-14km/liter and i have a 2000 civic which has same engine as 96-98),the parts are very cheap as a friend bought 4 doors 1 trunk 2 fenders in 20000 rs.and it runs great on CNG as well(my civic gives me 145-150 km on full cylinder and u should also consider that my car is automatic and automatic cars are a bit heavy on fuel
Best of luck