9.2 Why this does not make A2+ useless

A2+ become sentinels for failure of the lower anti-layers themselves. To formalize this, introduce a readiness/success gate r_k(t).

r_k(t)=1 if anti-layer k is available and successfully able to fire when its trigger is satisfied

x_k(t)=r_k(t) * product(1-x_j(t), j=0...k-1), for k>=1

Here x0 is the monitored positive structure. This model preserves the literal trigger while allowing high-order activation when earlier anti-layers are themselves silent or unable to respond.