Ironically, anarcho-syndicalism is the only flavour of anarchism that has needed to supply anarchist units fighting a war (Spanish Civil War), and it could do that.

Their system? Representatives from different plants regularly convened, discussed the inputs and outputs of their production, made agreements and resolved disputes. There was a market, a more transparent market than capitalism can provide - and the actors on this market had a democratic mandate from workers. Sometimes they traded for money, sometimes they exchanged services or goods directly.

However, there was also a government in the background - fighting on the same side as anarchists, with no power to spare for cracking down on syndicalism until much later. I wish I knew what they did when some plant became “indebted” to another or failed its promises. I don’t know if historians have written about it.

As for scaling - yes, transparency and trust don’t scale infinitely. If the partner in a deal is distant in some way (geographically, politically, otherwise), one may not want to discuss everything with them.