Now I definitely don't entirely support this idea, but consider this:
If you have a complete and matching set of robots and/or weapons, then they get various special bonuses that suit them.
There would be different boosts based on if you had the weapon set and the robot/titan; if you had 4 matching weapons like 4 Blights on a Khepri, then you would get a small bonus, something more unique or not in the game, like +50m range, or -.5 seconds cooldown.
If you have a matching set that has a robot/titan to be aligned with, like Gendarme/Cuirassier Ao Ming, then your bonus would be bigger. Say, maybe your weapons have a faster reload, or less time between shots, or a larger ammo count?