For now, the Creature type changing ability appears to be relegated to Esper colors (with Omo, Queen of Vesuva adding a splash of )
If an effect causes a creature with changeling to lose all abilities, it will remain all creature types, even though it will no longer have changeling
Steve Warner was asked about it in a Q&A
Be warned: This stops everyone s spells from being countered, so win the turn you play it if you run it out in cEDH, or you might just hand the game to another player
One and two mana Wolves and Werewolves are important, because creatures you play the turns preceding Tovolar can immediately attack and draw cards when you play Tovolar on Turn 3
But I can see an edge case where it could be a useful addition to a 60-card deck