Clearly an integration with the XHTML 2 modular schemas would be desirable but I had issues getting them to work with my tools, hence the 1.0 integration. Perhaps it would be helfpul to provide more than one profile?
The XForms 1.1 specification says ""A host language is expected to add attributes such as xml:lang as well as an attribute, named class, that holds a list of strings that can be matched by CSS class selectors." However, the XForms 1.1 schema does not include a class attribute. The intention seems to be that this attribute will be supplied via the host language integration. The approached used in the attached is to use the XForms schema verbatim--so it is not modified from a copyright perspective--and then redefines it so it incorporates the XHTML UI attributes.
Testing this script suggests there may be error(s) in the XForms 1.1 schema. The specification states "Core form controls always have labels directly associated with them as child elements— this is a key feature designed to enhance accessibility" [where core forms are listed at http://www.w3.org/TR/xforms11/#def-core-form-control]." However, it appears in some cases the schema requires labels for non core form controls where the spec does not, e.g., for case and group. Thus, a label is required for the case element per the schema; but there are examples of it in the spec without labels.
FYI, I also attached an ant script to validate XForms instances using the schemas.