A soft delete is definitely better than a hard one for the time being.
Would it be possible to see which of the decks in your collection have been soft deleted? It would make it much easier to manage your own collection that way.
Maybe a secondary list on your profile page with 'Replace' and 'Remove' options for each one -
- 'Replace' would allow you to pick a different deck and trnasfer your personal collection info onto that new deck (number owned, personal title etc)
- 'Remove' would simply romove (hard delete) the deck and associalted data from your collection
If you can give slightly simpler tools to collection owners, along with the soft delete, you might not need the more complex intelli-delete...