There hasn't yet, but you can change tiers on a level to get items early, kind of like how BOSS RUSH and Arena Duels does it.
"Filename": "Arena_0_Tutorial",
"Root": "Arena_0_Tutorial",
"Name": "Sleepwalker Gauntlet (FULL VERSION)",
"NameShort": "Sleepwalker Gauntlet",
"Description": "As a part of a versatility training regiment, a few tapes labeled <color=yellow>\"Unit Duels\"</color> have been left with this sleepwalker bed. It'll put you through a series of duels against increasingly strong enemies.\n\nAre you strong enough to handle it? Come find out!",
"Tier": 5,
I changed it to 5 instead of 3 unlike the usual of arena duel's, but I suggest changing it to 15 to get most of everything if not everything, like how boss rush does it.

Or alternatively make your own personal mod with the madcard maker, which I still don't know how that doo hickey works, but you could do that.

The place where you can find Arena Duel's stuff is over here
C:...\steamapps\workshop\content\488860\3276971658