I would really love to have the ability to link important (non-blood related) profiles to my ancestor's profile, similar to the way other media is currently attachable.
This would allow users to keep links to important people relevant to the target profile. For example, if it is known that an ancestor rented land from a certain lord, it would be useful to have that profile linked to the ancestor's profile, with a small description explaining the relationship.
Similarly, it would be useful for attaching god-parents, adopted children, commanding officers in the military, family servants, apprentices, business partners, and a large number of other important links that will aid users in truly understanding how people relate to each other.
This feature should also allow for the creation of profiles which are unlinked to any tree directly straight from the new 'link non-family member' dialogue.