I think there should be new weapons with more specialised uses. Most weapons now are just 'general-purpose' weapons that fit in well in most builds (the meltdown and needle blaster seem to fit this description ), but I think there should be weapons that are best used in specific situations to give you the advantage in battle. The addition of 2v2 and 3v3 battles is a great opportunity to add these. Here are some ideas.

Charged Plasma Rifle
Mythical, 60 Weight
3-5 Range, 3 Knockback
40-60 Electric Damage
-25 Energy Damage
**Damage and energy drain increase when one of the enemy's mechs is destroyed**
-28 Energy and +22 Heat Per Use
2 Uses Per Battle

Slime Cannon
Mythical, 72 Weight
3-9 Range
**Shoots goo that disables walking/jumping for 2 turns**
-18 Energy and +16 Heat Per Use
3 Uses Per Battle

ok but highly unlikely that that will be a recent update