Interfacing between workbooks (Exporting data Table and key properties)
Just looking at your function there 2 ways to improve it:

Public Function GetDataArrayFromSheetByCodename(ByVal strCodeName As String) As Variant
  Dim ws As Worksheet
  For Each ws In ThisWorkbook.Worksheets
    If ws.CodeName = strCodeName Then
      Set GetDataArrayFromSheetByCodename = GetTableRange(ws)
      Exit Function
    End If
  Next ws
  GetDataArrayFromSheetByCodename = CVErr(2042) '/ #N/A error
End Function


When having LOTS of sheets, this may be faster, but uses an error:

Public Function GetDataArrayFromSheetByCodename(ByVal strCodeName As String) As Variant
  On Error Resume Next
  If Len(ThisWorkbook.VBProject.VBComponents(strCodeName).Name) = 0 Then
    GetDataArrayFromSheetByCodename = CVErr(2042)
  Else
    Set GetDataArrayFromSheetByCodename = GetTableRange(ThisWorkbook.VBProject.VBComponents(strCodeName))
  End If
End Function


Also as a quick-inprove just add Exit For after your wsWasFound = True to not loop all sheets that are left after you found a match.  

For the second version of the function: I use the fact that errors inside of conditions inside of If-statements are always true when using On Error Resume Next. Len(....Name) = 0 Then normally NEVER can be true when there is a need of a name. But having an error inside will act like the whole statement is true. So it simply tries to catch the item. If it exists, it also has a name this way Len will be &gt;0 and be false (now your calculation will be done), else (it doesn't exist) it will act like If is true and the = CVErr(2042) will be set.
For the Subs: they doesn't make sense to me. What do they do? As it looks to me, they do simply nothing.

Last hint: You may change the function to As Range. When set a variable to it, you later could simply check by If Variable Is Nothing then. So there would be no need for = CVErr(2042).

EDIT
just to show the way i would hand over the values (while im pretty sure you will not use it)

Public Function GetDataTableHeaders() As Variant
GetDataTableHeaders = Array("Client Name", "Client Name", "Income", "Frequency", _
  "Date Paid", "Base Month", "Wrapper", "Ascentric Acc #", "Account to pay from?")
End Function


then simply set a variable to it or directly use GetDataTableHeaders(2) to get "Income"... as it looks, you may want to output the values to a sheet as headers and this way it would be much easier. However, you want to make it "not understandable" in some way, and for that it will be better to stay as it is right now :)