Workflow parameters in case of "no-code" workflow

I am using declarative workflow which consist of only .xoml and .rules files.
I use CreateWorkflow(XmlReader workflowDefinitionReader, XmlReader
rulesReader, Dictionary<string, object> namedArgumentValues) method to create
workflow instance. Since my declarative workflow is implicitly derived from
SequentialWorkflowActivity, I can't add any properties to workflow. Is there
any way to access namedArgumentValues, passed in CreateWorkflow, within
workflow or its child activities?

P.S. Actually I can add whatever I want in my workflow designer. But the
problem arise with property binding. For unknow reason, property binding uses
static type information to obtain workflow(activity) properties. So tricks
with ICustomTypeDescriptor or with overriding some methods in designer don't
work. I can add dynamic properties, but I can't bind to them. And in case of
workflow properties, which are supposed to be initialized by arguments passed
to CreateWorkflow, it breaks everything.