My vote goes to Bao-Dur. Canderous doesn't seem like the sort to marry....Or get involved in a relationship no matter what the fan fiction writers say. As for HK...no.
What might be unique would be to have Exile in a relationship with a non-party member (possibly non-canon) chap. Personally, I think most of the writers have used the other pairings and then some. just my two credits.
"Raking is easy, but all you get is leaves.
Digging is hard, but you may find gold.”
“Like a gold ring in a pig's snout is a beautiful woman who shows no discretion.”
"Get thee gone from my gate, thou jail-crow of Mandos!"
-Feanor to Morgoth