I forgot to mention that I went ahead and finished the mod like a year ago with the simpler system based on bricks.
I still feel like I owe you, by the way.
Anywho the damage function is
function Armor::damage(%this,%obj,%sourceObject,%position,%damage,%damageType){}
in T3D.
What you can do is just check the %damagetype( if(%damageType$="RRNoPlayerDamage"){return;} or something like that) and block if its a certain damage. Damage type is set in the projectiledata. If I remember correctly you can directly access Armor::damage in scripts/server/player.cs.
etc etc.