The company I worked for up until a little over a year ago tried to do something like this. They had a generic site builder (built with hokey 1999-era tech) wit

The company I worked for up until a little over a year ago tried to do something like this. They had a generic site builder (built with hokey 1999-era tech) with industry-specific templates and a whole bunch of themes that could be applied more or less orthogonally to the templates. It's not a bad way of doing it, but their execution was a little off and they weren't able to make it profitable over the nine years that I worked there. To do it profitably probably means doing it on a very large scale and in a way that doesn't result in huge hardware/maintenance nightmares (i.e. as little dynamic content as your customers will tolerate).