let query alter know which autocomplete it was called from

we have multiple solr custom searches on our site; these are all driven from separate search paths. so when the search is run we do an _apachesolr_modify_query() and based on the url of that path, modify the search query (for example, remove node types from the search results).

the issue is that we use autocomplete on all of these and the results that are returned are always from the full site index because, even though autcomplete is nice enough to run the
_apachesolr_modify_query hook, there is no way to know which form element is calling the autocomplete function.

i would guess it would not be too tricky to add in the form id to the json parameters and pass this along with the autocomplete request so that we could match the specific query alters.

any ideas?