Nether Wars starts at level 110. Players at that level may have a few million BR (as low as 300K BR is allowed!) and are expected to compete against players that are literally over 1,000 times stronger than they are. This is nuts. It is unfair to the player and unfair to the team that player gets placed on.
1: Scale everyone to the same BR. This makes the 1-on-1s down to team/skill synergies. Whales & more experienced players will still have an advantage, but it gives newer players a more sporting chance. This would also make Nether Wars a way to test out various team layouts.
2: Go rock-paper-scissors. Everyone is assigned one of three signs. That sign will be strong against one sign, weak against another, and 50/50 against the same sign. The signs then determine winner/loser in 1-on-1s, not BR.
Example: Bob is rock sign, Sue is paper sign, John is scissors sign, and Rick is rock sign. Bob vs John: Bob wins 100% of the time. Bob vs Sue: Bob loses 100% of the time. Bob vs Rick: Bob wins 50% of the time. There would then be two people with each sign on each team.
An interesting tactical twist would be if both players are the same sign, have both players lose.
3: Give some kind of edge to lower BR players. One such edge (that should be easy to implement) would be allowing lower BR players a chance to completely evade being attacked. I would do it based on the percentage difference between the two BRs, then if the evasion is successful, the defender cannot be attacked again by the same player for a period of time (probably 3-5 seconds).
Example: Bob with 5,000,000 BR attacks Sue with 4,000,000 BR. Bob has 25% more BR than Sue does, so Sue gets a 25% chance to evade being attacked completely. If Sue successfully evades. no fight happens and Bob cannot attack Sue again for 5 seconds.
The evasion chance probably should be capped somewhere between 50% & 90%.