The ion cannon / nuke seems to be z-axis specific, actually (meaning height DOES matter). In the Under map, I planted a beacon below the hill (in that tunnel that leads to the tiberium field). My friend (on the enemy team) deliberately went up onto the sniper hill, stood in the exact center of the beam... and not a thing happened to him.I don't know if the same thing will apply if the beacon is HIGHER than the target, will have to try that sometime.
It's easy to plant a beacon, but it's hard to keep it from being disarmed unless the enemy team are idiots. Engineers can track the "beep-beep-beep-beep" sound right to the beacon and then disarm it.
I too disagree with the pedastal idea... it'd make the beacons useless. A tiny little pedastal would be so easy to mine, just like the MCT.