Suggestions:
1 - In the Vault tool, create a "Deck Maker" with dropdown lists to only show cards that the team has in the vault and a "Quantity" column that restricts input to legal card counts for the deck.
*This would provide another layer of illegal-deck-checking to the process and be really super cool.
EDIT: Revised after CuCN's comments, below, about reasons for tool functions I had suggested to change.