Previously when deploying Windows you could use the command 'control.exe intl.cpl,,/f:"languages.xml' with some funky xml identifying what keyboards you wanted, with Windows 10 this half works so you don't really want to use it.

So what do you do?

Well there is a powershell command Set-WinUserLanguageList, however that only applies for the current user logged in. This could be ok as a logon script but if you don't like them and want the language bar set for all new users there is one more trick you can use!

Firstly, log on to a Windows 10 machine as admin and set up all your desired keyboards then open Control Panel\Clock, Language, and Region\Language ( control /name Microsoft.Language ) and click Advanced Settings.

Update:  Before doing this we need to clear out all of the default user registry This will break new user logins, it's just to cleanly get the registry data we need

load up regedit.

Then under HKEY_USERS\ click File\Load Hive

Type in C:\Users\Default\Ntuser.dat

Call the key DefaultTemp.

Delete all keys then unload the hive from the file menu

Then click 'Apply Language settings to the welcome screeen, system accounts, and new user accounts'.

In this window click 'Copy Settings' then choose 'New User Accounts'

What this does is load the Default User registry hive and insert some values into a preload key Update:  and some other areas. This is all well and good for the current computer but we want this done during OSD right?

So load up regedit.

Then under HKEY_USERS\ click File\Load Hive

Type in C:\Users\Default\Ntuser.dat

Call the key DefaultTemp.

Export the key 'HKEY_USERS\DefaultTemp\' as DefaultKeyboards.reg then unload the hive.

Create a SCCM package with the reg file. This will be used during OSD.

In your task sequence we then need 3 Command Line steps.

1 Load Default User Registry

reg load HKU\DefaultTemp "C:\Users\Default\NTUSER.DAT"

2 Install WIN10-Keyboards

Using the package created

REGEDIT.EXE /s DefaultKeyboards.reg

3 Unload Default User Registry

reg unload HKU\DefaultTemp

4 Test

Update:  Some languages need the associated Language Features from the Windows 10 Features on Demand iso to function correctly so it is best that you install all the features related to them
Basic, Fonts, and OCR.

You can script the installs using dism. Example:
Dism /online /LogPath:C:\Windows\temp\AddLangPackage.log /Add-Package /PackagePath:Microsoft-Windows-LanguageFeatures-Basic-ja-jp-Package.cab /PackagePath:Microsoft-Windows-LanguageFeatures-Basic-zh-cn-Package.cab