I first heard of the concept of Popcorn Turrets from the Developers at Petroglyph (if you dont know, these are former Westwood guys who made CnC, Dune 2). They were designed for the Wraith Faction of the Shadow Revolution meant to support thier hit and run playstyle by having turrets that are cheap and deploy quickly to help hold or even assault a position when they don't have the time to wait for big expensive slow to build turrets. Basically put Popcorn turrets are designed to be cheap and pop up fast but are also commensurately very squishy and have low DPS with the intent on players building multiple. If applied to the Hive Spire and Thorn Spire I think that would work better for Aliens, they have a lot of territory to cover and so can't afford to pre-defend all their weakspots. I would reduce the Cost down to at least 350 (+/-50) for the Thorn and Hive Spire, build time 15 seconds (+/-5), cut down the HP by 2/3, attack speed reduce by 1/4, add a clip size of 10 for Thorn and 20 for Hive, running out the Clip will cost another 1/3 of their attack speed. Also the Hive Spire would be Lowered to T1 and Thorn Spire to T2. All these changes will really help differentiate them from their Human Counterparts and plays into the Aliens style better, relying on ambush and swarming rather than on pure defensive power.
Support Spires should be added to help Aliens hold a Position and generally aid the Alien commander and troops. Each Support Spire will cost between 1,000 and 2,000 biotics and have about 60 seconds of build time like the turrets have now.