I think technically it will become really hard to prevent nodes B,C and D from communicating with each other and to ensure that "cloned" attack transactions do reach the targeted nodes before the targets exchanged their states. From attacker perspective I see a design flaw with this attack caused by the fact that you have to keep all "A" nodes synced as long as the attack lasts. to be able to do so you have to identify which nodes communicate with which to not broadcast "anti attack" transactions. for me the flaw for this attack is that after the attack has begun you have to make sure that your nodes stay up to date in "their network segment" which is "undefined" and therefore impossible. you may create dynamic filter maps since you know which transaction you receive from which nodes (B,C and D) but you would have to be really lucky to be able to exploit the traced communication routes since this requires you inject lots of correctly ordered valid transactions. if you assume that the network consists at some point of about 100-2000 nodes and each node broadcasts their transactions to 16 nodes and so on you would have reached with a intermediate network latency of 250ms all nodes within 1 second (1->16->256->4096). so if your A nodes try to branch the balance states within their network segment to cause a network hold there is almost no way.