My guess is that the Bricoli was used by ancient peoples at the time. It would more likely have been used by non-Graeco-Roman cultures as the Greeks and Romans at this time had access to advanced Gastrophetes, Ballista's, Scorpion's and other devices. The more backward barbarians would have used something like the Bricoli in place of these. This is a WAG. The barbarians didn't write the books!

The Onager looks wrong! It should be replaced by a scaled up Ballista or Scorpion.

Some information on ancient siegcraft;
Catapult/Ballista;
It is interesting to note that the largest stone-thrower on record, a three-talent (78 kilogram) machine, was built by Archimedes.
This light torsion catapult was the most common type of artillery during the Hellenistic period. With only slight modifications the weapon was employed still in the Early Roman Imperial period, up to ca. AD 100, when the Romans redesigned their artillery. The word catapult derives from the Greek katapeltês and means ‘against shield’; it is an antipersonnel weapon initially and most catapults remained that; they were not often fired at walls with the intention of knocking the wall down; they were fired at the top of walls to keep the defenders heads' down while a ram attacked the wall below. Stone-throwers were built from mid fourth century BC onward, but only after serveral stages of development the mature standard type of the palintonon appeared in the third century BC. The reconstruction sketch drawn after the text of Philon, Belopoeica shows a heavy palintonon for throwing 1/2 talent (ca. 13 kg) stone balls. The total weight of this weapon was about 3 metric tons, the weight of the elastic ropes of the two torsion springs alone ca. 330 kg. In contrast to the euthytonon the palintonon could easily be dismantled into the main components: the two torsion springs with their wooden frames, the long stock (table, ladder and slider) together with winch and pulley, also the carriage. Because of the heavy weight and the sheer size of the palintonon dismantling was indispensable, otherweise the machine could not have been transported over the often poor and narrow roads of Antiquity. The stone balls were fired generally in a flat trajectory, not in a high one as often mistakenly assumed in modern literature.

The two-armed torsion stone thrower was still employed in the early Roman Imperial period. The Roman author Vitruvius provides a description of the palintonon under the latin name ballista (X.11: De ballistarum rationibus et proportionibus

Field artillery;
The first reference to and possibly use of artillery in the field (rather than around a city in a siege) is in 354: Onomarkhos the Phokian deployed them against Philip II, Polyainos 2.38.2. These are ‘stone-throwers’; probably non-torsion like that designed by Charon (dates unknown) as described in Biton (C3? BC).

http://www.swan.ac.uk/classics/staff/ter/grst/What's%20what%20Things/artillery.htm

http://www.newton.mec.edu/Brown/TE/C...ations.htmlnot very good but perhaps useful for animations graphics if we decide to use these.

http://antique.mrugala.net/Rome/Ball...0catapult.html