I would like put it this way.I think you need to consider a No.3 batsman just as important as openers,if not more.I think I'll have to go with [MENTION=79064]MMHS[/MENTION]'s idea about having a left right combo at top and Babar being better against pacers than spinners and Fakhar being better against spinners.
So my first 3 are going to be:
Considering Sharjeel comes back:
Tests:Sami Aslam,Azhar Ali,Babar
ODIs:Sharjeel,Babar,Fakhar
T20s:Sharjeel,Babar,Fakhar
Without Sharjeel:
Tests:Sami Aslam,Azhar,Babar
ODIs:Fakhar,Babar,Haris/Umar Amin
T20s:Fakhar,Babar,Saif Badar/Amin
In PAK team, only Babar has the quality to play long, long innings & do a proper pacing; which none of the other openers including SK or Fakhar has. Previously, MoHa had it to an extent in Asia, while Azhar & Shehzaz never can accelerate with time on wicket. SK & KAkmal are opposite - they don't have the technique (& stamina) to bat for 35+ overs, rather they are effective with short bust - 23 ball 35 (Or say average of 35 @ 120 SR in a 7 match series) is the best output for them. Fakhar is still new, in PSL as well he didn't last longer after Power Play - but his List A Stats of 50/90 tells that, he can be tried at 3 for better combination.
I always like to pick inputs from history & try to fit that into strategy. More or less, what I have seen is historically, best/most successful teams had the best 2nd wicket partnership - that's only possible if one of your top 2 most complete batsmen bat at 3 & other one opens. Viv-Grineedge/Haynes, Majid/Sadiq-Zaheer, Marsh/Boon-Jones, Tendulkar/Sehwag-Ganguly, Smith/Gibbs-Kallis, Haynes/Simmons-Lara, Mark/Gilly-Ponting, Hayden/Gilly-Ponting, Sanath/Kalu-Hary, Dilshan/Sanath-Sanga, Astle/dot-Fleming, Gambhir/Tendulkar - Sehwag, Warner/Finch-Smith, Sharma/Dhawan-Kohli .......... Only PAK/PCB played Anwar/dot-dot-MoYo-Inzi ...... And latest Ahmed/Azhar-Babar-MoHa ........ Even AB's spot of 4 is one slot too low - ideally it should have been Kok/Amla-AB, which would have won SAF more meaningful matches. In history of PAK cricket after Imran, probably those few years PAK's ODI bating was most dominant when it was like Anwar/Sohail-Inzi; then they pushed Inzi down to promote a wood-chopper at 3.
Ideally, SK & Babar should open with SK being given free license. He should never bother for average, rather should look for 2X + Y = 175+ sort of stats. Here, X is batting average & Y is strike rate - that's 25/125 = 175; 30/120 = 180, 20/140 = 180, 50/100 = 200. For an aggressive opener, 25/130 is a fantastic stats, if his partner can manage 45+/85+. Babar should play for milestones (but, obviously not Tendulkar way) till 35th over, for a stats like 55/90 (that's 200 which is the stats of the best in contemporary cricket - AB, Kohli, Smith, Root. Viv & Zaheer's sum was 185 & 180, when outstanding would have been 160 (40/80) - that's why those 2 are always my top 2 ODI batsmen - ever) while Fakhar has to play most critical role - tempo of his game'll be adoptive to bat for different situations like 10/1, 100/1 or 200/1. At present, Azhar has only one gear, while MoHa's teeth on the gear wheels has wired out. No. 3 is the most dynamic position, whose main KPI is adoption to the situation - Babar was the best for that, but Fakhar can manage as well & he gives better combination at 3 with left-right-left-right (& left, if Haris/Amin bats at 5) batting order (& his spin play) - that order is effectively worth extra 5-10% runs, for the constant change of bowling line & extras (& captain being stressed to set fielding to avoid slow over-rate ban).
PAK'll need their bowlers to bail out even against AFG or WI in most times, if the top 5 has Fakhar and all 4 of Azhar, Babar, MoHa & Sarfraz - in which ever order.