What if the hydralisk and/or the mutalisk would be the evolution of a different unit that has a similar role instead of being evolved from a larva? This can be done in many ways and I will give a small example later in this post but first I want to explain why I believe this would fix some problems. The main problem we have with the zerg atm is that they are too much similar to what they used to be in SC1. Why? Because too many core units are returning. The main problem is that no one is really willing to replace any of those units because they are all iconic and loved units. I believe that making 2 of those main units (the mutalisk and the hydralisk) an evolution form for a weaker unit we would be a nice compromise between adding something new to the race and keeping what players like at the same time.
Here is an example of how this could be done:
Avianling
Mineral: 25
Gas: 50
supply: 2
Build time: 10
Mutater: larva
Requires: spire
Special note: 2 from one larva
Hit points: 40
Type: light, biological, air
Damage: 3 w/o splash
Speed: fast
Target: ground/air
Special ability: can suicide on friendly units to heal them
Evolution into mutalisk cost:
Minerals: 75
Gas: 50
No additional supply cost
Morphing time: 13

