Currently we can use snmp, Zabbix Agent and (some) simple items as discovery checks.
I'd like to see the functionality expanded so it will be possible to call external scripts to perform network discoveries with.
This would allow a pluggable way to extend the discovery process with some more advanced processing.
For instance, we could create a script that does a reverse lookup of an IP address to a hostname and return the name as a value. In the actions we can then specify a name string as a match value.
The same functionality could be introduced for Zabbix modules.