Hacking Is it possible...?

There's only one "MIOS Slot" on Wii.
Installing a new custom MIOS will replace the old one, so you don't need to uninstall first.

If you want to be clean, you can install the official MIOS v10 first, then install either DIOS MIOS (USB only) or DIOS MIOS Lite (SD only), depending the device you will place your ISO to.
 

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