Strong should no longer dislike it it when the player picks a lock. Pretty much the only reason why I never recruited him before.

Works with both unowned and owned locks.

He will still talk as if he dislikes you lockpicking, but his affinity won't change, and the affinity notification doesn't appear.

Not tested with any DLC, but it should work for them as well, since it removes the entry from his list of approvals/disapprovals.