When you monitor many servers through differents proxies, you need to be able to set up trigger dependency against proxy.
But, as far as I know, there's no way to automatically get the dependency setted up.
First point: since some servers are monitored by a proxy and some are not (typically zabbix SQL servers), I just can't set up dependency inside the template or I'll have to have one template per service per proxy.
Second point: as far as I know, there are no macro available which represent the proxy monitoring the host and even if there is, I don't know how to implement following rule:
"For a given trigger, if the host is monitored by a proxy then trigger depends on proxy availability; if the host is not monitored by a proxy, then there are no dependency against proxy."