Implicit trigger dependency when monitored via proxy

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."