Thanks for the suggestions.
I'm not sure what you mean: "DSLRs seem designed around mechanical controls", and I'm not sure it's relevant. As long as the camera provides control via an electronic means (e.g. USB port as some do), then a good user interface can be built on the outside of the housing, it doesn't matter how the camera was designed.
I wasn't suggesting a broad multi-purpose housing, but something specific to a model line, such as the Nikon D200, D300, D300s, where gross physical changes are minimal, but there was enough change in detail that the D200 mechanical controls in the housing won't work for the D300.