Thanks for the replies all.
I thought that might be the case.
I have a possible, limited case solution, but I haven't tried it yet.
I might be able to make a shader that will multi-sample a large image, and give roughly the same effect as C2's native multi-sampling.
The drawbacks are that the image would have to fit in frame at it's large size as any part of it off screen can't be sampled I believe. That means that it's size orientation and position would all need to be handled by shader. That said, it could conceivably give multi-sampled results in a "point sampled" project, so it could be handy if it works out the way I think it might.