I'd like to submit this as a possible Datasheet for the Mega battle;
Necron AA Obelisk 80 Points
Unit: 1 AA Obelisk
Type: Tank
Armor: F(11), S(11), R(11)
BS:4
Weapons: 4 Turret Mounted Gauss AA Cannons
Special: Counts as Immobilized, may arrive as per Deep Strike rules
Gauss AA Cannon: Range (72), Str (6), AP (4), Heavy (2), AA Mount, Gauss
My model for it was the Hydra, basically subtracted something, then added something to keep the point cost similar, for example; I immobilized it, but gave it deep strike. I also tried to keep it with the Necron feel; armor 11 all around because everything in the Necron codex has the same armor on all sides. I also changed the guns to 4 heavy 2 cannons instead of 2 twinlinked guns because so far nothing in the Necron Codex is twinllinked. So instead of 4 attack dice that you can re-roll misses, I just have 8 dice. I then took away a str point and added Gauss (because all necron guns have it).
I then added 5 points to the cost just to be sure.
What do you think?