CSB Nickname Manager puts an admin in control of names. amx_rename <target> <new name> writes the name straight into the client's info-key buffer (through fakemeta) and then locks it for csb_nick_locktime seconds, so the player cannot switch back mid-round. Separately, a reserved-name list — admin, owner, console, server, root — is enforced continuously: anyone using one is renamed to a generated Player_<id> so nobody can impersonate staff.
amx_rename <name or #userid> <new name> with immunity-aware targeting.csb_nickname_manager.sma and drop it in addons/amxmodx/plugins/.plugins.ini and change the map.amx_rename needs the ADMIN_SLAY flag (d) by default.