Had a few thoughts on improvements (most notably projection minimap, but I see that's been addressed) but one thing I miss from TA is the good ol' coastal battery. Right now there's no defensive structure capable of defending against bot spam - lasers and such are just a bandaid because their range is limited and it's just a matter of time before they're overwhelmed, and the heavy artillery structure is slow and inaccurate with too much emphasis on point damage over AoE to put a dent in a swarm, not to mention fairly expensive and level 2. I always liked to have some coastal batteries force-attacking a chokepoint (the lack of those is a separate issue) but just being able to put up something with some range using a level 1 constructor would really help a lot. Firepower and accuracy similar to the artillery units, but with a good bit more range.
Defending was never as easy at it is now. Pelter already got buffed and now shoots a huge lot faster. What do you want the game to be? Planetary Turtelation? Loads of laser turrets, some arty and walls can easily cope with medium sized bot groups. And when theres a 500 bot deathball running over your base, the fault isnt the "weak" defenses but the fact your opponent had enough time and resources to build it.
In since alpha, seems you missed it. Its built by all T1 fabbers. Sheller and that T2 arty bot are somewhat useable as anti turret units.
There are many units still missing so wehave to wait and see..I'm pretty sure there will be a t 1 arty.
To be honest, dont even seriously start it. Unless you get extremely lucky and no one attacks you for a long time its bound to fail. You can build as much turrets and arti as you want but when you control 20% of the planet and the opponent 80% he just crushes you with his much larger economy. Either by rushing with insane ammounts of bots or just spamming nukes faster than you can produce anti. In PA, resource income is one of THE most important factors.