What I ended up doing is below because other options simply didn’t work right, and there is limited documentation on versions 1809 and 1903. Maybe I can save you some headache.
MDT "Add Language Packs Offline" referenced in original comment, does not appear to work with newer versions of Windows(1903)/SCCM(1902 and later).
Other options such as adding Language Packs(and other features) using dism /online after OS installation results in the Windows UI remaining the default EN-US language. resetting this setting via Powershell and rundll/xml proved unsuccessful.
Download the required language packs for my environment. Inject them directly into the offline install.wim via DISM
NOTE: in MS Volume Licensing site, DO NOT select 64-bit or 32-bit when trying to download the Language Packs. You must first select MULTILANGUAGE from the language dropdown, or you will only have 1511 language packs available to download.
Create an answer file, My answer file is attached for reference.
(EDIT)Add Language Collection variable to "All Unknown Computers" device collection, and leave value blank, and uncheck "do not display this value". Screen shot below
This will add the Language variable field when your start the image process
Set Language Variables using the Set Dynamic Variables after Apply OS but before Setup Windows and Config mgr (screenshot below)
I added a step to use English by default if none of the rules proved true
I created a package containing all the new language features for each language, Each package with a bat file that runs the series of dism commands (example attached). NOTE, some of the languages do not contain the speech capability.
Added Timezone support using tzutil /s “Timezone name” and keyed it on NTDomain.ClientSiteName attribute (screen below)
EDIT: I forgot to include the Language Collection variable on Unknown Computers collection