User blog comment:IamJakuhoRaikoben/Chapter 439: Albareth Empire, Review./@comment-1776824-20150608225247/@comment-24277053-20150608234800

I think Erza was made guild master because Hiro wants Team Natsu to know about LH, if say Lexus was here and named guild master, and it was Lexus that Mest was taking to see LH, Natsu would have left well enough alone, but because it was Erza, someone on his team, he had to know the little snooper.

As for Erza going or staying, if we have a guild alliance and Kagura and Minerva are part of it, Erza will be needed to keep the peace between the two of them, mainly from Kagura towards Minerva.