I actually propose a one-up on this:
Allow players to link their legacies together for relationship purposes. Naturally, this would be agreed upon by the players and only possible between those who are on each others' friends list.
I play with my husband and I'd rather like to drag his character into my legacy and link our characters. If TOR were to, in the future, offer some sort of housing this could be combined with that function. For example, a player could make a Legacy-based building and only characters linked into that legacy tree could then enter that building.
This would not affect any legacy based perks, it would only be socially pleasing.