There's a guy in California who has successfully replicated The Turk (legendary automata that played master-level chess; beat Benjamin Franklin and caught Napoleon cheating), but he refuses to tell anybody how it works and says he'll have it burnt when he dies.
Siege engines this small, this slow, this brittle and no doubt this expensive would be any use of the battlefield. What you gain in portability you loose in rate of fire and power.
It wasn't till the arrival of the M-66 that true battlefield superiority was obtained. There were, however, a few issues that still needed to be worked out with the unit.