If Ren Xiaosu wanted Melgor to become the leader of the Prosperous Northwest's branch office, he would first have to let Melgor gain the capability to take on this great responsibility.
However, a sorcerer's growth was gradual. In other words, Melgor would have to go through countless meditation and spell training sessions before he could become a true archmage.
On this point, even if Ren Xiaosu gave the black Eye of True Sight to Melgor, Melgor would still not be able to become an archmage in just a few short months.
Besides, Ren Xiaosu could not bear to give all his Proficiency Stones to Melgor either. After all, he could use these 90,000 Proficiency Stones to directly turn himself into an archmage. Even if he wanted to complete the important mission of accomplishing the Prosperous Northwest 3.0 plan, he could not possibly donate the Proficiency Stones just like that.
But it did not matter. Pretension could make up for the lack of ability.