Plusle and Minun should get a third partner for triples. It could be called something based off of a Neutron. It could have an ability that does minus for a partner or plus for partner. And they should all get an evolution. A stronger version making them better for singles.
Pokemon Black FC: 3653-9864-6035 Pokemon White FC: 4641-8614-2897 (5th Gen Edits only)