As mentioned by @Matthew , "We are not planning to implement this functionality at this time." But As suggested , you can download the MSI and execute it from powershell to install Azure AD connect. I haven't tried installing AD connect it but something like below should work:
$file_path = "c:\test"
$log_path = "c:\test"
$machine_name = Invoke-Command -ScriptBlock {hostname}
$date = (Get-Date -format "yyyy-MM-dd")
$msi =@('C:\test\installer1.msi','C:\test\installer2.msi')
foreach ($msifile in $msi)
{
Start-Process -FilePath "$env:systemroot\system32\msiexec.exe" -ArgumentList "/i `"$msifile`" /n /passive /l:c:\temp\epson.driver.wrapper.log" -Wait -WorkingDirectory $CurrentLocation
Start-Sleep 300
}
Reference: https://community.spiceworks.com/topic/507906-powershell-to-install-exe-and-msi-package
How to install .MSI using PowerShell
Hope this helps, feel free to tag me in your conversation.