Much of the early game issues I have playing alien early game is that a lot of the human units can both attack from range and move faster. In contrast, crabs are slower, fragile, and melee. Fragility can be countered with just having a lot of them as an artificial hp sponge to close the distance. Melee isn't an issue if a unit can survive long enough to close the distance which is also solved by having more of them. However they can't close the distance if they are also slow in combination to being fragile and melee.
Crabs could use a speed buff to help them close distance with range infantry units while maintaining their fragility so that ranged units can gun them down.
The game could benefit from removing starting units that are not tier 1 ( we all start with infantry and crabs. No hunters, impalers, or light quad). Light Quads ( when controlled by a player and not just yeeting themselves to death ) are just a tad bit faster than hunters which means we run into the same issue of the hunter getting kited around in circles. Unlike the crab, it wouldn't be appropriate to give the hunter a speed buff because they are stronger than buggies so being slower makes sense. Removing high tech units from the start helps alleviate this. However in addition to that, the aliens could benefit from impalers being a bit cheaper to build so that they can more effectively use them to shoo light quads away from their base.
Here's the changes this causes:
-Infantry can no longer kite crabs whicih means they need to be present in large enough numbers to gun down crab rushes. This means commanders on both sides need to be smart about engagements. Too few infantry get attacked. Too few crabs cannot close distance to attack.
-light quad harass is still possible, as they can dart in and out to attack and pick off crabs. But it's no longer a game winning strategy, as they have to be aware of where the impalers are placed when doing this.