I'm sorry for writing this in public forum, but Eloy doesn't get messages from anyone who is not current contact and doesn't reply in the tracker issue.
Hi, Eloy. We are currently working on implementation of you proposal in MDL-24359 - i.e. https://tracker.moodle.org/browse/MDL-24359?focusedCommentId=404241&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-404241 We have some questions about function you proposed blocks_get_instanceids_for_context. Most important what is expected in "$filter" argument and in which format. Is it for filtering by block type of something else? Do we correctly understand that $recursive=true means "this context and all it's subcontexts"? Also it would be good if you suppose a place where such function should be added (class or php file). Time is pressing, please reply in MDL-24359