Zabbix at the moment has three levels of macros:

• global macros
• template macros
• host macros

I'm proposing:

• add yet another level of host groups macros between template and host macros
  Best place to add such feature in zabbix web frontend is http://zabbix.server/hostgroups.php?form=update&groupid=group_id
• it should be possible to track inheritance of the macros (probably best place would be http://zabbix.server/hosts.php?form=update&hostid=host_id -> Macros tab) that some host macros are overwriting template global, template or hostgoup macros