If you open with Arshaf you're forcing a proper batsman down the order. And in T20s, it could result in that batsman not even having a chance to play. Could be the waste of a batting option. On the other hand if you play an extra bowling option instead, you've got 6 full time bowling options and part time options. Wasting a bowling option, and making your batting weaker (which I don't think is necessary, we have 5 very good bowling options already, a 6th arguably wouldn't even strengthen it but would weaken the batting).
Afridi is a bit different, a vastly more experienced batsman playing in a domestic team. A lot of the batsmen he played with had less experience internationally or were arguably worse. But I think we can find 7 batsmen in a entire country who can bat better than Arshaf.
Arshaf is mainly a bowler, who should be picked on basis of that. I don't think it's a great idea picking him in a batting slot, if we already have full time bowling options from 7-11.
I would rather move up Babar to open where I think he'll be more suited, don't think he can effectively accelerate the innings at 3, while opening he can set a platform at a decent rate. Out of the squad I'd rather bring in Umar Amin who has a very good domestic T20 record, 30.80 at SR 121 is very good. And he can be a handy part timer too. Nothing against Fahim, but with the bat given Amin's greater experience and time batting I have more faith in him performing with the bat than Fahim, especially higher up in the order.
I don't think makeshift openers who are bowlers really works too well. Guys like Afridi are exceptions (and even then wasn't a great international opener) who had more talent with the bat than ball, and had more talent with the bat than most of our specialist batsmen.
