Battle Wars
A mash-up of Battle Grounds and Alliance Wars...
Both players place 3 defenders from their 40 champ deck on a 3 'tile' map. Each tile has different nodes, maybe based on existing AW nodes, or a mix of AW nodes, BGs nodes and new ideas. Nodes could change each season or each week or each ranked 'Tier' to keep the mode fresh.
Both players pick 3 attackers to fight the 'Battle War' based on the opponent's 3 defenders and nodes. Fastest player to KO all 3 fights wins. Attacker health remaining each fight used as a decider.
Each player can ban 5 of the opponents champs before the match starts. There could also be season wide global bans or 'Tier' specific bans, etc...
Similar health pools and time limit to BGs to keep it fast paced. If you get KO'ed in a fight you can revive (resource dependent), but obviously lose time.
Rewards based on winning a Battle, moving up 'Tiers' and End of Season placement. You only match players in your 'Tier' until you progress to the next 'Tier'.
Happy to hear your thoughts on this 'very' rough idea.