The existing forms designer feature does not fully implement the XFORMS standard and misses basic features (eg user specified submit). This results in proof of concept applications looking bad and newcomers to Intalio spending much time and effort getting around the limitation. Moving from Proof of Concept to productive development then requires a rebuild of UI.
Rather than spending effort in developing the Forms Designer to a useful level, this proposal suggests the adoption of Orbeon Form Builder which appears committed to full function forms.
Basic requirements:
XFORMS templates conforming to the existing UI as starting point for user form design.
Vaildation of the Intalio build requirements (Input/Output instances etc)

There is a side benefit of taking this approach ... any true XFORMS-based development tool would interface with the Intalio Design and Build.