The thing with the DSTWO that surprises me, is that they haven't yet made a firmware patch for the DSTWO which can 1:1 emulate a 3DS card bus with the I/O it has hooked up to it.
It'd be simple in theory. Boot into DS mode to load a game chooser, choose the game using a plugin application. When you choose the game, it sets a boot-mode flag, reboots the 3DS (powers off the DS), disconnects and reconnects the card-slot bus, and pushes the encrypted 3DS card data across.
The DSTWO then shows up as the selected 3DS game. When you reboot, it'll switch back to being a DS-mode flashcart, and load the DS/3DS game chooser again.
The DSTWO is already seemingly capable of 1:1 CARD emulation, it's how it loads the DS-mode bootstrap/whitelist faker (a fragment of Alex Rider: Stormbreaker which satisfies the checksums) before loading the DSTWO plugin menu, as well as being able to load certain DS games regardless of anti-piracy (albeit, without cheat menu/savestate support).
It'd be simple in theory. Boot into DS mode to load a game chooser, choose the game using a plugin application. When you choose the game, it sets a boot-mode flag, reboots the 3DS (powers off the DS), disconnects and reconnects the card-slot bus, and pushes the encrypted 3DS card data across.
The DSTWO then shows up as the selected 3DS game. When you reboot, it'll switch back to being a DS-mode flashcart, and load the DS/3DS game chooser again.
The DSTWO is already seemingly capable of 1:1 CARD emulation, it's how it loads the DS-mode bootstrap/whitelist faker (a fragment of Alex Rider: Stormbreaker which satisfies the checksums) before loading the DSTWO plugin menu, as well as being able to load certain DS games regardless of anti-piracy (albeit, without cheat menu/savestate support).