Maybe this is why Brynjolf and Karliah, when it became clear that a new Guildmaster would be needed, were so quick to stick the newbie with the top job. They didn't want to lose all their respect and charisma, which is inevitable if you become Guildmaster.
Not at all. Delvin addresses you as "boss". And sometimes Vex greets you saying "The guild master graces me with a visit, what can I do for you today?"