Ok I made a map for ESF incorporating the idea to test it out, no bots, no other players, just me.
First of all the framerate drop wasn't significant enough to make me disconnect, but you could notice it and I run a pretty mean machine.
The model gibs were 'rock' but you could use a custom one, rock didn't really work well as they were tiny rocks compared to the huge slab I destroyed as the first layer.
On core destruction there were no lights, flashes or party hats (i'm too lazy) but i'm sure you could add them in via triggers and multimanagers etc.
The HP idea did work as you'd expect, but heres the downfall.
Discs (On Ultima's point). I used Krillen's. Not only did it destroy the first layer, but it went right through the second as well. >.< One more and the core was down. Argh. The disc size doesn't matter as the target is enormous. Solution? Add a new custom entity to the esf fgd that acts as a breakable but with larger gibs of the same texture as the brush with the entity tied to it and make it take a set number of damage from discs and nullify the 'continous penetration' (lol) rule that they follow to protect the core. You could also have a flag (tickbox) to damage anyone who touches it (for the fiery core) It would probably still cause a lot of framerate drops and I don't know about lag, though i'm sure it won't be pretty. Make the layers smaller (I was trying to work propotional to the gif)
Anyway, two thumbs up for the suggestion and the suggestions to the suggestion etc :yes: :yes:
And to contribute something useful, you probably wouldn't have the whole team attacking, some could attack the core and the rest could attack the defenders to stop them swatting away all the balls or beams, while the defenders could try their best to keep the attackers in melee so they can't shoot the layers.