It would be a heck of a lot easier just to use a custom DNS that redirects that URL to a custom server – but that won't help because it is a secure connection (hence "https") and it won't connect to a server that lacks the right cryptographic signature.
The old Nintendo WFC had a similar problem that was only circumvented because Nintendo made a big mistake when it came to making their secure connection certificates. I have some vague understanding that before that major discovery, there were hacks of Mario Kart DS that removed the secure connection and made it feasible to play online – but making major hacks of low-level 3DS software would not be the same.
Or at least that's my understanding.
