Interesting idea. Perhaps that external arc accessory could be brought back to serve as the global shield generator. Emitters aligned from top to bottom... perhaps it fans out to provide a few arms around the entire sphere and a way to connect the energy shields (instead of having to 'control' the shape of the energy shield into a jupiter-sized sphere)

: I'm
: thinking like the style of energy shield from the Shield Wall in Halo 2 or
: the anti-Flood shielding in Halo Wars. It'd be really cool to go visit
: those generators. Heck, same with the hard light generators. This just
: really feels like a structure with a lot of rich potential for cool
: backdrops in a Halo game.

Just got me imagining what the sphere would look like from the inside on one of the discs in its defense configuration! Layers of platforms, hard light core at one end, spherical inner surface formed from the discs' inner walls. O_O

: The fact that only a few hundred thousand Forerunners lived on this thing
: boggles my mind. I guess teleportation helps where the distance is
: concerned, but still... seems like a waste. I really wonder what they're
: doing with the rest of that space.

Construction perhaps? Other life forms? From the games we do know like lots and lots of empty space :P
But yeah, 100,000 beings on a construct 100,000km in diameter is very, very weird... A metropolitan city is but a tiny speck on its surface. hm.