I've had some sucess building up to 2 extra armouries, in ATCS with skilled people.
The whole reason they work, is that they have a backward psychiology on the aliens. ("Wtf, 3 armouries, how retarded, no use in taking them down)
The thing they forget is that the armouries is severely hindering their movement possibilities around in the human room, blocking the line of sight into the guts of the base, and making a staged defense that still has almost all the turrets covering all the 'stages'. (my base core, with reactor and nodes, always has 3 turrets covering it, as well as a lot of turrets spread out in the room to extend human dominion over the room, which makes it harder for the aliens to camp for kills just around the corner.)
While this is not really any better defense wise than the good 'ol defense corner sandwitch in ATCS, it is BY FAR better for the human freedom of movement, range of dominion... Actually controlling the whole base room helps a lot in pushing out.
Also, rants tend to kill the armoury, and then run away or die, most of the defense remains intact, and i can rebuild when they run away /die, or cramp into the corner if things get hairy, slowly retracting my defense into the corner while still safe between my semi-blocking armoury.
Of course, this demands a lot from the builder, as the whole base strenght lies in that you have the time to adapt the base even during an attack, but I like it.
It also is better in terms of teambleeding/blocking and general retardedness.
But it is far less self sufficient than the usual base.
I just get so freaking tired of the same base every damn game, and camping the turrets with your rifle because if you try to leave the turret wall, you are instantly mauled by the tyrant around the corner.
As for SD, Arms can be rebuildt during SD, turrets can not, which may help you reinforce your defenses after having pushed back that tyrant rush, even during SD.
I'm not saying this is the best, or even any good at all. But in my experience, it is by far a viable variation from the same, bland base that is always built.
Btw, I build on 100BP servers, and have been building standard bases for a long time also.