Tyger only talked about what content could be soloed when the game was live after someone else asked about making a solo emu.
The way I see it, there are certain posters here not simply suggesting a standalone CoH game is possible and easy to make, but instead asserting that as an absolute fact - and then considering any reasoning to the contrary to be off-topic and not contributing to the discussion.
So I'll follow that rule, and tell you two ways that a standalone CoH client can be made:
1) You'd have to write a separate game server application that runs on the local machine, but only supports one player connection, and can fool the stock CoH client into connecting to it and accepting commands. It would have to contain duplicates of a lot of the content from the CoH client so it knows what the client knows, in order to command the game so it behaves like it should.
2) You'd have to re-write the CoH game client in a new game engine, and import and re-use or adapt all of the textures, sounds, objects, scripts, and design it so it no longer requires a server.
Sticking to the same rule, I'll let you judge for yourselves how difficult or easy those would be. It's not easy for *me*. Maybe it is for someone out there.