dude, if a little z-axis is giving you trouble in a game that takes place IN OUTER SPACE then, idk... maybe you shold read some books on submarine and naval tactics. Play some Homeworld.
First off, HW is my favorite game of all time, so I'm plenty accustomed to working in 3 dimensions. Second, as I said, the problem isn't the Z-axis, it's the SB's inability to fire along the Z-axis. In HW, a defensive force (since there weren't platforms, at least not in HW1) could engage a fleet above them just as well as they could a fleet in front of them, so that argument is invalid. Even mines from minelayer corvettes would go up. As you said, it is in outer space; what's preventing it from firing upward/downward, relatively speaking?
EDIT: To clarify, I am NOT angry at the player who did this, though I initially was, obviously. I am angry at an obvious flaw in the functionality of the TEC and Advent SBs (being as the Vasari have conviently dodged this bullet). This is what I'm trying to call attention to. I do not want to get rid of the Z-axis, I just want it to be available to everything, including defensive structures.