Perhaps the most fundamental Element of the Game Type (not the map) is the conflict between the Spartans and Elites - a conflict between Species rather than Teams. Supporting this is another fundamental Element of the Game Type, the Fire Team. Within each Species are three teams known as Fire Teams. Both the Species and the Fire Teams are core constructs of the Game Type which are heavily exploited by the Play List maps.
If I told you the game was multi-team of 2v2v2v2v2v2, you would immediately understand that there are a total of six teams. And while it is true that there are always six teams in Invasion, a better way to describe the Fire Team construct is 2/2/2 v 2/2/2. From their Initial Spawns to the Core crossing the finish line, each Play List Map treats each of the six Fire Teams as six individual teams, not as two large teams.
We see this concept in the Initial Spawns being out of line of sight with each other in every case except Breakpoint Invader Initial Spawns; with each Fire Team having their own Respawn Zone, even when they are located next to each other; and with Bro Spawning only within the framework of the individual Fire Team. Grasping this concept of six teams, three against three, will help you forge your Invasion map to treat each Team as an individual Team. This in turn will help your map present the Game Play of Invasion.
For both Invaders and Defenders, the Teams on the same side of the map that the Alpha Objective is on are typically referred to as the Alpha Teams; the Teams on the same side of the map as the Bravo Objective is on are typically referred to as the Bravo Teams; and the Teams in between the Alpha and Bravo Teams are typically referred to as the Middle Teams.
In a typical Territory Tier, the Alpha Team attacks the Alpha Objective, while the Bravo Team attacks the Bravo Objective. This forces the Defenders' Alpha and Bravo Teams to match the Invaders'. Now that the Defenders' Alpha and Bravo Teams are separated from each other, the stage is set for the Invaders' Middle Team to outwit the Defense Middle Team and move toward the Objective that the Defense Middle Team is NOT moving toward, helping their fellow Invaders capture the Territory with simple numerical advantage. This divide and conquer strategy facilitated by combining Dual Objectives with six teams is one of the fundamental Game Elements that makes Invasion vastly unique from any other Game Type.
Summary
Invasion is about two Species in a conflict, and six Teams representing those two Species.
The Play List maps were forged to demonstrate an awareness of six individual Teams, not two large Teams, and so should yours.
The three Invaders Teams can divide the three Defender Teams between two Objectives to overcome one of the two Objectives with a numerical advantage.