I like Saini as a bowler and i think he could do very well in the international cricket. May be it would be good if he's training under likes of Dravid or Zaheer so that he could learn to keep his emotion and raw pace in check otherwise Virat's influence could turn him into another Umesh Yadav in the limited over cricket.
Both Dravid and Zaheer are known as mild natured and I don't know whether Saini would be able to adjust working with them. Aggression, up to some extent is good. But when someone repeatedly bowls beamers directed at the batsmen and then refuse to apologize, then the term is not "aggression". It is more like bullying rather than aggression. Saini is not the fastest bowler in the world. We had legends such as Curtly Ambrose, Alan Donald, Glenn McGrath and Courtney Walsh in the international cricket scene two decades ago. They never bowled intentional beamers even once in their career. But that didn't prevented them from winning matches for their team.