It'd cool to have him play some tests. I'm all for it if he has a decent record.
I think in the modern era a lot of fast bowlers have a choice, either play LOI or play tests. Doing both is tough. Amir's already going to cut down on tests. Hasan I feel will do the same, he's had injury problems of late.
I wouldn't mind him playing over Amir. Amir's been lacklustre in tests of late, and what's the point if he's only going to play the odd test series or two.
Feel we're starting to get a problem, where if you're good enough as a pacer you play LOI. If you're not, then you settle for tests. LOI gives more money, good prospects for domestic leagues, world cups participation, less injuries and arguably more fame (as people in Pakistan care more about LOI these days).
These guys like Sadaf, Hamza (and recently Abbas) might be the way, guys who dominate first class cricket, who don't really seem like prospects for LOI cricket (at least currently). They'll give 100% in test cricket, and know how to manage themselves over 5 days without breaking down, and don't completely rely on their pace to be effective (Riaz was an example of this). Think the days of tearway fast bowlers in tests are gone. Even now, a lot of teams only have one really fast bowler, and often to allow them to play they have to sacrifice LOI games. In asia even worse conditions for fast bowlers as they'll get run into the ground on those pitches.