I think you can use a cyclocross bike for more than just "real light" touring. Those frames are tough and stiff. If it can handle the abuse of a cyclocross event then I'm sure 50lbs of cargo will not be a problem. Think of it this way: If you weigh 180lbs would you not let your 230lb friend borrow your bike? It's all about weight distribution. If your bike lacks the proper pannier mount eyelets then go with a Bob trailer or the like.

Here's a shot of a cyclocross bike just like mine doing touring duty: