I strongly believe, that there are a lot of players out there, they dont want to rush through hundrets of pvp fights to reach a top place in the pvp-rankings. These player like/love gems-of-war and wants to play the game reguarly without grinding, but solving puzzles insteat.
So here is my idea:
- Every week a challenge trail opens, where you face x-preset teams (for example 4). There is an entry-fee (diamonds), coz the are some nice prizes can be won. Or the first try every week is free and every next ones cost a fixed or incrasing amount of a fee.
- You dont fight with your strong own upgraded teams. No, insteat you have to create freely (not like in arena) a team form a limited card-pool BEFORE EVERY FIGHT. The limited card-pool contains (for example) 50 cards, each card has their own level and their own number of unlocked traits.
- You only have one try to beat each preset team. You can choose freely in wich order to fight the teams.
- If a player manage to beat every team, GoW accumulate the team values the player used. These ATV (accumulate team value):
Option A: goes into a ranking and the ranking determine the prizes at the end of the week (like in pvp).
or
Option B: will be compared to some set values. The lower the ATV is the more prizes the player gets instantly. (more like in arena). - You can throw in addintional bonuses (vary from week-to-week) like, when a player finished the trail within a number of rounds (nice twist), or used no 3-traited cards or uesed only 3 mana-colors, or …
For me, something like that sounds a nice challenging puzzle, i can do every week. It reminds me of spending hours in a character-creation-screen of an rpg-game 
What do you think?