Most of the problems that everyone is sharing about Mehran are to do with the build quality. I have the pleasure of keeping a Mehran 98 and pain of buying a Mehran 2005. You cannot imagine the difference of feeling in driving these two vehicles.
Mehran definitely has a way different ride than the other cars and you ofcourse will not find it to be feature rich.
However it costs less, serves the simple purpose of commuting between two points with ease, and extremely cost effective in maintenance.
I have used my Mehran as MPVs many a time. Just a couple of weeks back I bought a split A/c which was not being delivered by the dealer on time, so took my Mehran to the Dealer and had all the pieces loaded into it (with ease. It was 1.5 Ton split).
I have taken my 98 Mehran to Northern Areas many a times, loaded with 4-5 gorwn up occupants without any issues.
If you use a 800CC engine to pull a car full of people and then try to use alternate fuel (CNG) then "Yes, It will under perform". What else would one expect.
Regarding Brakes, I agree they stink especially when you have other people (more load) in the car. At high speeds they would even refuse to help you stop. But this is not Mehran, Its the manufacturers feeding in sub-standard parts.
Lack of quality and quality checks plus efforts to mantain manufacturer margins (against inflation) are the factor why today's Mehran is not such a good car as it used to be, but it still is a viable option for hundreds and thousands of customers, and it definitely has its selling points.