By downloading a current client.xml and mapping it local, you can make changes to the client.xml and get other items to drop instead of the lockboxes. But there is no way to get those new items to save to the server. At least I haven't found a way yet. Been messing with it all day and can get things like 50 Unstoppable Lockboxes and full Gear Sets to drop, instead of the lockboxes, you can even see them in your storage, but the game gives a cve after a while and on refresh, nothing is saved.
And before anyone asks, its by changing the RewardId's in the client.xml for the Group boss you are trying to farm. (Example: If you are setup to collect Loki lockboxes, you would need to change the Kurse Group Boss RewardId's)
Again, this will make other items drop, but none of them will save. You can see them, you can even equipt them on your agent, but as soon as the game refreshes, they are gone. If they are other type of lockboxes, as soon as you try to open them, the game CVEs and on refresh, they are gone. This is not a working drop any item hack.
If someone can use any of this to help figure a way around the CVE, and get the items to stay, let me know.