i got this idea playing in tjw's server, were you don't have enough space to put all the turrets you can build.
How about having a item stand?
Can be stacked
Armored (take longer to kill, like reactor)
A human can jump on one (make a staircase, etc)
doesn't need to be near reactor/repeator
doesn't explode when killed
available for about 2 points
Alot of maps already have blocks to build on, bue being able to decide where to put them would be very useful.
Another reason this would be good is that you can stuff 4 or 5 acid tubes together, and they don't interfere with each other's line of fire.
s1, of course.