If you want to have it localized, make a Desktop.ini backup from
NLTmpMount0?\Users\Default\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Accessibility
...and copy to:
sources\$OEM$\$1\Users\Default\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Accessibility
If you want to delete only, add this command to Post-Setup page:
del "%systemdrive%\Users\Default\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Accessibility\On-Screen Keyboard.lnk"
...else if you don't want to have the shortcut removed and an empty folder, use this command instead to remove the folder and shortcut:
rd /q /s "%systemdrive%\Users\Default\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Accessibility"