Hi Johan,
At the moment you can set the class for all the fields on a form. Or you can set it at the individual field level.
Setting it at the "type" level would involved a _lot_ of template settings and properties (both at the global and procedure level) because there are lots of types. Some types are "complex" meaning they have multiple parts (each part can have it's own CSS.) It's probably do'able, but perhaps not something I'll be doing soon.
cheers
Bruce