Frankly, I don't want Hasan Ali anywhere near the Test team. I'm 100% sure he's going to be mighty successful but playing too much cricket with the usual, tightly packed schedules that we have, I'm not sure he's going to be able to last very long.
Firstly, you don't want him to succumb to injuries.
Secondly, even if he doesn't get injured, playing 5 day cricket, PSL, T20i's, ODI's and what-not is going to cause a massive reduction in pace. Hasan was consistently 143 KPH + in the West Indies series but we saw a reduction in pace (not a massive one) in the CT because of the amount of cricket he's played recently.
Third, Hasan Ali - while being a fast bowler - is also sort of a mystery bowler and you don't want to burn him out. He's going to be found out sooner or later, like (most) other bowlers but to make sure he's doesn't become innocuous just yet, I would let him have a good burst of LOI cricket before making him a regular Test feature.
Lastly, I personally think our Test bowling lineup is not too bad. While I despise Abbas for his lack of pace (sorry), he's taken wickets. Mohammad Amir has been amazing recently maybe you can bring Junaid back. He has experience of playing Test cricket and wants to play the longer format.
I also think we should give more youngsters a go. Playing a couple of different bowlers for every format isn't the end of the world. England have been successful with this approach. There's no point of having world class bowlers half fit (Starc, Boult, Shami, Mustafizur) but play all formats.