Help choosing the final unit

I've nearly finished building to 1000 points and need help with the last unit.

So Far I have 20 deathwatch veterans, Artemis, a Watchmaster, Draxus, a Corvus Blackstar and a Rhino.

What would be a fun/useful unit to get to round me up to 1000(ish) points.

I'm currently leaning towards a squad of sisters and converting the Rhino into an Immolator.

For now I'm planning on sticking to 1000 points whilst I finish a couple of other projects.