While they are prevented from attacking until there are seven or more cards in exile, he does encourage these effects with an ability that lets you draw cards when one or more cards go into exile from the graveyard or the battlefield
Find the English versions of Battle Partners cards in Journey Together.
Looking at which themes offer the strongest and most flexible options for support within the Commander card pool, instants and sorceries are the clear winner
Suffice to say, Boltund V is a very, very good boy
If you really wanted to reinforce Unions as a whole to compete with the current meta: I would say something like "Target 1 Union monster from your hand, Deck, or Graveyard: Special Summon 1 monster whose name is included in the card text of that card from your Deck or Graveyard
This option allows you to replay Story mode with all previously collected cards and the same World Championship progress