We have what I imagine is a fairly common problem, but cannot find a workable solution.

We need a way to tag a model group that is used to define a unit type for a residential building. The unit types repeat throughout the Revit file and are used to define rooms that should be consistently numbered using a suffix based on the model group. e.g. if I have a unit with a bathroom and 2 bedrooms, I always want the bathroom to have the suffix "B" and the bedrooms to be "C" and "D".

We have the code to number the rooms in the units sequentially based on the model group used to define them. So for the one unit, we number all rooms starting with 101, the next 103 etc. But I haven't found a way to define parameters within the model group that can consistently define the suffix for the room tag.

What we've tried:
  1. Use room area to define the suffixes. A simple solution, but not customizable if we want meaningful suffixes.
  2. A custom family (generic model) used as a hidden tag. This could work technically, but the team rejected it as it interferes with other standard tagging methodologies.
  3. Using a model line with custom properties stored on the model line entity. This works if the model lines are defined and tagged outside of the group then copied in, however this is too tedious to maintain. Ideally we want to be able to edit the properties directly within the model group - but I believe that's not possible based on this link: The Building Coder: Editing Elements inside Groups

Are there any other tricks we can try from either the GUI side or the API side to work with custom parameters within a model group?