It turns decently, but pretty slowly, not able to hit fighters.
But it uses only 8 of the smallest engines.
I wanted to add extra armour to the arms, but wanted a light version first to see how it handles.
The armour is heavy aluminium btw, makes it easier to see than iron.
It's powered by 2 second level reactors.
Now the arms mainly look cool, I bet it would turn faster if I got rid of them... but then i would loose cool points... tough decision.
Making a roll version is doable(and i probably will), but won't that make it weaker as a defence turret? it will have a much harder time tracking a target, won't it?
And yes, they are dirt cheap, I started from a new save, and got it built in 30 min. this includes mining for the drill etc.
And size is totally variable, just add more guns in a checker pattern, and longer arms.
EDIT: and oh yeah, I accidentally place the engines so it would just spin around on the first try, got to 20 m/s of rotation pretty quickly.
It was hilarious!
And also, with two arms shot off, this thing will still turn around in any direction(providing i still have one horizontal and one vertical arm left)(albeit in a circular motion)