Normally I would say to create a powershell script with the additional language cab in it. And configure all settings you want in that powershell script. as example

DISM /Online /Add-Package /PackagePath: .\lp.cab
Set-WinUILanguageOverride <xx-xx> (where xx-xx is your language culture)

And convert it to a win32 app and deploy it as an required app during autopilot esp?

Could you show us what you have tried until know?