It should be possible to give custom permissions to users/groups more detailed.
On the current version of Jenkins it is not possible to split administrative functions.
For example, I would like to allow some users to access update center to execute the update of the Jenkins and also install new plugins, but not allow to change proxy configuration, or even worst change authentication configuration.

Today to the allow a user to access the plugin manager page I have to give the user the permission called "Administer", so if I allow it, the user would be able to change all the Jenkins, including remove my permissions from the system.