Study Design in XML (SDM-XML): what is still missing?

Last year, our CDISC volunteer team published the "Study Design Model im XML", an extension to the ODM standard, filling some functionality gaps (i.e. study design features I was already asking for for years) of the existing ODM standard.
We are now almost a year further, and have had the time to implement the SDM-XML in our tools (such as the ODM Study Designer). We also tested the model against many use cases (even as a possible replacement for submitting study design information to the regulatory authorities).
So it is now time to make an inventory.

We found that the model is already used (or has been prototyped) intensively for searching for possible subjects for studies using patient information such as from EHRs (from the inclusion/exclusion part of the model). We also found that our "workflow" model of SDM-XML can easily be transformed in BPMN-2-XML, which is the generally accepted standard for workflows. This e.g. allows to import a clinical workflow into a hospital information system (HIS) and integrate it with the workflow of the patient care.

There are a few things however that are still failing in our model:
- subactivities: i.e. activities within activities. For example, there can be an activity "place an ambulatory ECG device", which itself consists of a number of subactivities. In ODM/SDM-XML this is not supported (yet). This also has to do with the lack of support for subworkflows.
- subworkflows: i.e. workflows within workflows. Building on the previous example, the activity "place an ambulatory ECG device" will consist of a number of subactivities which need to be executed in a certain order, and maybe with some forking or branches, so needing a subworkflow.
- swimlanes. Those knowing a bit about workflows do also know the concept of "swimlanes". For those who don't, I could try to explain, but wikipedia does a much better job  here.

In order to implement swimlanes, we do however need "roles", such as "primary investigator", "study nurse" or "monitor". We don't have this in ODM, we only have the concept of "user" (which is in priciple a person) with a "UserType" attribute. The latter could be used for "role", but this could better be avoided as its current enumerated list is just too limited and not adequate.

So we would need to extend the ODM further than we already did.
At the same time, we have the problem that "StudyEvent" (for a visit) is not a good concept anymore. In SDM-XML, a visit is essentially a container for a number of activities, which can be datacollection activities or activities in which no data is captured (such as placing the ambulatory ECG device). If we allow activities to have subactivities (and subworkflows) isn't a StudyEvent nothing more than an Activity?
Also (in my opinion) we should introduce an element "Role" in the "AdminData section" of the ODM, and allow to assign roles to "Users" (P.S. A person can have one or more roles).
This could then allow us to introduce the concept of "swimlanes" in the workflow part of ODM/SDM-XML.

I do already have a list of other wishes I have for ODM.
If we find the necessary (human) resources, wouldn't it be time to start thinking about a future ODM Version 1.4?

Let me know what you think!