One area to expand the game into is the set-aside area. Right now, there are very few cards that interact with set-aside cards, and fewer ways to get something back that has been set aside without a turn limit. Ideas off the top of my head:
David’s Raids
5/0 Red TC GE
“If used by a WC hero, discard opponent’s top two cards of deck (put LS in play). Set this aside. If you make an unsuccessful rescue attempt, you may topdeck this.”
Mary Sister of Martha
7/5 Gold Hero
“Each opponent reveals 2. Put LS in play and set aside the rest. May band to Martha. Cannot be interrupted.”
God’s Provision
3/3 Multicolor TC GE
“You may draw 1, or heal a hero, or add up to 3 of your set-aside cards to hand.”
Blastus
Acts 12:20 (for those of you who want to know where I got this obscure name from)
3/2 Gold evil character
“If blocking, you may place a NT Gold evil enhancement from hand, discard, or set-aside on your Herod. When that Herod enters battle, play the enhancement.”