Hi,
answer is : not easily…
In my view, best way is to change BooleanEvaluator on titlebar.jsp to and replace with a permissionevaluator (after you need to determine which permission is needed to see administion icon)
Then, you need to modify Admin Authentication Filter (AdminAuthenticationFilter.class) in web.xml and replace it by your custom filter which allow appropriate people.
I had same problem, i needed that some local admin can manage groups and people. Finally, i don't modify all this but i use an external way to manage it with an LDAP import (people and group). Like this local admin manage it with an external tool (Outlook)
I hope this can help you…