Currently when you edit a recurring event, all occurences are edited. Instead, you should be able to select "All", "From this occurrence and forward" and "only this occurence". Also, in all of these cases, past events should never be touched.
Behind the scenes this is done by splitting the events into two, one edited copy and one unedited original (unless you select all, and there are no past occurrences, in which case the original is edited).
Also, you should be able to simply delete only this occurence, all occurences or all occurences from this point forward. The same restrictions to past occurrences apply.
