Hm. Most of my ideas center around [the zerg] being able to reproduce them [zerglings] like [the] hive does drones. The point of a zerg rush is to cripple your opponent at the beginning, giving yourself a head start. Waste to many points on this, and it will end up even...
It all depends on how you want to play it really...
EDIT: Either bump the attack of the zerglings up to 3, or cost down to 40. (2 attacks of 6 for 50 pts per squad, or 2 attacks of 4 for 40 pts per squad.)
I think the first will convey the feel of a true zerg rush better than the latter, but it may be a little over powered...