Territory class would be OP'd, as would CBN, but I think Cannot Be Interrupted would be wise from a gameplay standpoint. If this was played, and then after a few additional plays it was negated, it would be an annoyance to have to remember all the LS's that were already there and those that were searched for. CBI non-battle winners are ok in my book.
So I would make it like this:
0/0 White Hero Enhancement.
Search all decks for all Lost Souls and put them in play. Negate special abilities on all Lost Souls this turn. Cannot be Interrupted.
John 4:35
"Do you not say, ‘There are yet four months, then comes the harvest’? Look, I tell you, lift up your eyes, and see that the fields are white for harvest."
Very nice idea.