Just readin' the new dex and realised something interesting... the Command Barge is a transport. Obvious, but think about it. Just because the model's rooted there doesn't mean the Lord can't get out, does it? So he can fly over a unit, deal three attacks, then get out.
After that, the vehicle shoots the unit. Then the Lord assaults because the barge is open-topped. The unit should now be dead; Lord gets picked up. Repeat.
I could easily see an army with two of these Overlords flying around in barges, swiping at small units and cutting them to pieces, whilst their royal courts deal with basic army buffing and maintenance. What do you think?
EDIT: I'd equip the Overlords with a Warscythe, Sempiternal Weave, Phase Shifter, and Res Orb just in case; if short on points drop the Orb.