In Craft 3, a plugin can listen to the
Element::EVENT_REGISTER_SEARCHABLE_ATTRIBUTES event to modify the searchable attribute list of an element before it is indexed.
Currently the answer is no.
Maybe it makes the case for some sort of
onBeforeSearchIndex event a plugin could listen to and influence what Craft adds to the search index, but given that manually updating the search index isn't meant to be a common occurrence (Craft keeps them up to date in normal element saving operations), I'd probably add the workflow you're using that requires frequent updates to the feature request.