Personally I think we're chopping and changing too much. We don't have any great talent in middle order, but got to make the best out of what we have.
I think we should forget about international average, should stick with the middle order bats who are consistently striking at a high SR. Guys who can score fairly easily from ball one, given our slightly slower, reliable top order is going to put them in that position 9/10 times. We just have to trust their PSL averages/performances (which should be the main factor, it's the only limited overs domestic with high pressure, good level bowling). There is no point playing potentially better, but slower SR batsmen who don't fit this team right now.
Really that would leave Asif Ali, Haider Ali and Iftikhar Ahmed who I'd just keep playing for now. Guys who have performed at PSL, and shown ability to score at high SR in internationals. They aren't amazing, but I think the best we have so far until someone new establishes himself through PSL and domestic. Maybe if we show faith in these guys, they can string some performances together instead of being constantly dropped and recalled.
Of course for no.7 position Imad should be there no question, he's far above the rest there.