Milhões de clones basicamente não são bons se você não puder transportá-los em algum lugar.
Esta é uma citação da novelização do Episódio II de Star Wars: O Ataque dos Clones:
"Master Sifo-Dyas requested the most powerful army in the galaxy. We have worked with only the best shipbuilders to fulfill that request." ―Lama Su
O romance é considerado canon, e a Wikipedia tem essa sinopse .
No romance de Star Wars Tarkin (também canon), há essa troca entre Tarkin e Dooku pouco antes do ataque a Geonosis.The Star Wars Episode II: Attack of the Clones novelization was written by R. A. Salvatore and published on 23 April 2002 by Del Rey. It is based on the script of the film of the same name. It includes much expansion of scenes and also many scenes which were cut from the movie. Some of them are original to the book.
Tarkin tried to decipher the count's inference. "One might almost conclude that you're positing an advantage to going to war. But how would that work? The volunteer security forces of the Confederate worlds against--what, Judicials and ten thousand of your former Jedi brethern?"
Dooku adopted an arrogant expression. "Don't be too surprised, Governor, if the Report has access to secret forces."
Entre essas duas citações, eu acho seguro inferir que, além de construir tropas, elas também estavam construindo o hardware necessário para torná-las um exército funcional.