Wasn't it "Asrar Ahmad" (Ibn-e-Safi) who actually "Created" Imran Series? Personally, Asrar Ahmad was the one who kept the series close to its original persona. Mr A-Hameed had his own writing style but given his seriousness in writing, i never really liked his writing of Imran Series (not to forget that he write magnificently well, when we talk about his other writings)
So after Ibn-e-Safi, Imran Series was best portrayed by Mazhar Kaleem's pen. The persona of Imran was kept close to original, and his "wit" and "sarcasm" was most noticeable in Mazhar Kaleem's publications.
Btw, hats off to these guys thinking. They had great minds. This is the kind of stuff we are seeing in hollywood movies these days and they wrote that stuff from their mind. Thats just Mind Blowing.