I've enhanced wikiplugin_googlemap.php and wikiplugin_googlemap.tpl as follows:
Support for specifying multiple items via:
All items must be of homogeneous type specified by locateitemtype.
Google map will now center and zoom to fit multiple markers if no default x,y,z are specified.
These modifications were done to 6.2. I looked for information on submitting patches but couldn't find how to submit for that version. If anyone is interested I'll provide the code / diffs.