Patriarchal blessings - digitized copies of blessings available to individuals based on current rules that are converted to business rules in the application - linked to records in the family tree online
Ordinance certificates - Aaronic Priesthood, Melchizedek Priesthood, Marriages, etc... - Certificates or copies are and have been sent to CHQ. Digitized copies could be available to the individuals involved and family members for their personal and family histories.
Other general Church history archival records - Subject records available and linked from individual and family records in the family tree. Example - My grandfather was a bishop in a ward - A link could be available from his record to any publically accessible but rarely accessed records from that ward, stake, region during the time period he was there.
Of course these ideas would require extensive organization of the database and a heavy-duty CMS. It would get easier as hopefully callings are stored and hopefully archived, records are digitized from the past, etc...
As has been mentioned in the SuperPAF / HyperPAF thread, ability to link to particular sections of pages in digitized microfilm records or other documents acting as source documents would be a welcome ability someday.