Being in Australia we get like 60% of all eshop stuff so on my 3DS I swap between Ireland & Australian eShop stores to save money / buy games unreleased in Australia. Trying to do the same thing on WiiU to get Mighty Switch Force, but it logs me out of my ID because the region settings dont match.

So my question, do I just make an extra ID like I have on my PS3/360, and will the game be available on my main ID, or do I just have to wait for it to come down under?

Yes, a second ID with the country you need. And you need to change your ID and your country when you choose that ID. So make sure you change your country before create the new ID to match the country.

I don´t know where the games are registered but all games are available to any ID you have in the system.