Not aware of any Trimble integration in ArcGIS Mobile, so I am not sure what question you are asking.
Subtypes in ArcGIS require integer values in the Code field while the Description field for that code value can be any valid string expression. As far as I know, there is no such restriction in data dictionaries in Pathfinder or Terrasync. Code values in data dictionaries can be up to 6 string characters and I assume associated Attributes that are visible to users have to maximum string limit.