QuickFixFactory.createAddMethodFix() provides a minimal version of the regular 'Create Method' intention, adding little to the existing PSI functionality.
The following featured are missing from the current API:
-selection of return type (through code-provided type information)
-selection of parameter types (through code-provided type information)
-expansion of method body template + default return value
Please prove API access to the existing, "full", Create Method intention.