Scripting

Add autologon to your sysprep for admin and then have the task run as a post task.

  <AutoLogon>
                <Password>
                    <Value>*****************</Value>
                    <PlainText>false</PlainText>
                </Password>
                <Enabled>true</Enabled>
                <LogonCount>1</LogonCount>
                <Username>administrator</Username>
            </AutoLogon>

or add it to your post task to autologin and run the task or poke to runonce to run it after reboot.

start /wait reg.exe add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\WinLogon" /v AutoAdminLogon /d 1  /f
start /wait reg.exe add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\WinLogon" /v AutoLogonCount /t REG_DWORD /d 2  /f
start /wait reg.exe add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\WinLogon" /v DefaultUserName /d administrator  /f
start /wait reg.exe add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\WinLogon" /v DefaultPassWord /d *****  /f

start /wait winpe

or

start /wait reg.exe add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\WinLogon" /v AutoAdminLogon /d 1 /f
start /wait reg.exe add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\WinLogon" /v AutoLogonCount /t REG_DWORD /d 1  /f
start /wait reg.exe add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\WinLogon" /v DefaultUserName /d administrator /f
start /wait reg.exe add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\WinLogon" /v DefaultPassWord /d ***** /f

start /wait reg.exe add "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce" /v Runwinpe /d winpe.exe