the only way to do so would be to setup a reverse proxy server and have it spoof the user agent. I would not recomend it tho as its difficult to do and nobody seems to have a guide for doing this for the average non technical person.
another possible side-effect of doing this is that it may mess up the eShop and Mii Verse.
the reason the eShop could get messed up is that (at least the Wii version is anyhow) the eShop is a webpage and the eShop (Nintendo's Web Server) will be expecting the user agent to be the normal Wii U one, not a spoofed one. I have not tried it so I do not know what exactly happens when the user agent is spoofed and how Mii Verse will function with it spoofed.