the 2X can be used in the wii
but.... you would be making a stupid move, the reason the 2X can be used in the wii is because you can just use the pads normally found on the 2. So essentially you'd just be using the 2 anyway for more money
So using the 2X in a wii is possible but REALLY stupid
Also you will lose the 2 pads and 10ohm resister on the 2 which allows you to perform the red standby fix:
"If the power light on your Wii is red when the console is off, meaning you do not have internet enabled and have WiiConnect24 turned off, then you may do the following installation to enable your lightbar to work when the console is off. If your standby light is orange, you can skip this step. The reason for this step is because when WiiConnect24 is disabled, then the Wii does not send power to the lightbar when the console is off. We remedy this problem by supplying power to the lightbar directly from the power supply.
To allow your lightbar to operate while the console is in red standby, you will need to remove the resistor indicated and then solder the two points shown to your PulseVU 2"