=o i actually think that if u can use the move every time you switch in, it just promotes hit-and-run tactics (you can revenge kill, but many threats such as victini etc can just come in and hit shit, then get revenge killed, then you go to another threat and ohko with a strong move).
Also in the meta we talked about, Meloetta Pirouette is useful since it can use Relic Song on the switch, is decently powerful and only wants to use it once anyway!