sounds like a great buff, the hot oil would be better against infantry, ballista basically a trebuchet+troop killer, but if you buff one we'd need an offensive buff to
^^^ In evony, You had traps on walls. Best way to kill them was to spam them with 100k spies. Easy and cheap to make, hella damage to traps and clears way for your troops.
but, i suppose even spies could destroy them, while on regular missions or all spies have a separate sabotage attack outside of the HoO could work here as well...but that might be stealing ideas if evony got their panties in a wad