Guess it's time for an analytical archive dive, then.
(deep breath)
Tempest in the Refuge would mostly benefit from Plavu'col Capitol. Both Tempest and the environment can easily deal lightning damage, so Tempest would end up healing at least 4 per round for as long as the Capitol is out. This would make Tempest very hard to kill. On the other hand, people playing Tempest in the Maerinyan Refuge aren't looking for a challenging game anyway.
In addition to Sky-Scraper, Abject Refugees and Freedom Fighters in the Dok'Thorath Capitol deck also don't have the Thorathian keyword, despite the card art depicting Thorathians. Perhaps that tag actually means "Thorathian Member of Grand Warlord Voss's Legion of Doom, Oppression, and General Unpleasantness", which is quite understandably shortened on the card.
Omnitron-X is most interesting, partly because there are more interactions with the device keyword, partly because it examines what happens when third party content uses keywords in unexpected ways (whether on normal cards or on character cards) - but mostly because Luminary runs on device cards, so any odd behavior arising from Omnitron-X would apply to Luminary. Searching around, there are significant interactions with Omnitron I (more when advanced), Omnitron IV, Baron Blade: Evolved Madman (advanced), and Baron Blade: Evolved Madman's Omni-Blade. There are also relatively minor interactions with Omnitron II (advanced), Ambuscade's Charged Attacks, and of course Luminary's stuff. Mechanically, none of those are any more bizarre or game-breaking than Luminary's use of that keyword in the same conditions. In the spirit of entertainment, Omnitron I would need editing, as no one wants to turn against Omnitron-X or Luminary when the game is effectively over.
(Side note: A Villains-style game with Omnitron I (advanced) + Omnitron-X (device) + Baron Blade: Evolved Madman (advanced) + Luminary + Omnitron IV is a doomed combo, yet it's amazing the way everything relies on each other.)
Otherwise, Omni-Unity from Oblivaeon could be a mechanical golem or a device or both, and Citizen Storm could be both a citizen and a Maerinyan. Normal villains Citizens Hammer and Anvil could have the citizen key, but that would be purely for flavor since there's nothing that would interact with it in normal play.
(Side note: Today I have learned that America's Cleverest Legacy's base power has no restrictions on the card it destroys, other than matching a keyword from a deck. He can destroy villain character cards. Of course, you can get the same results with any character at any time by putting the cards back in the box and watching a movie instead.)