As far as responsive designs go, there are far to many different options for that to be feasible from a wizard like form builder.
with a responsive design, you need to define what the design will respond to, then set all of the dimensions for that response.
To implement that in a wizard style interface like form builder would maker it overly complex and cumbersome to work with.
In future version of Data Bridge we will looking into a server side approach to responsive designs like WURFL. using the server side approach will allow you to create a design for each device, then use the WURFL device detection to deliver the corrrect design based on the device being used to access this site.
as for fluid layouts, you really just need to replace width and heights with percentages, and font sizes with ems. This can be done for the most part with form builder as it stands by editing the form design.