Well, considering there was very little that couldn't be done solo in the game...
Which just shows how little you understand about CoH. Although the maps and unchangeable data resided on
your computer, everything that made the game work, that is, the re-enterable game code, (which controlled everything from the NPCs to where you were on any given map and allowed you to interact with the environment, spawned NPCs and other players), resided on the
server. This is the "server code," which is the Holy Grail. And although we refer to it as the "server code" as if every game server was, in fact, a
single piece of hardware, it is quite likely at each of the titular "servers" (Virtue, Freedom, Protector, etc) was, in actuality, 10 physical servers working together. So just for starters....can you afford that much hardware?