Those interested in the technical side of emulation on Windows Phone compared to Android should
read this earlier discussion. But I would agree that the DS is within the capabilities of Windows Phone, unfortunately the technical obstacles are sufficient to prevent any simple port of an Android or x86 emulator for a fifth generation console. To create EmiPSX the developer had to completely rewrite the core of the emulator, which requires in depth knowledge of the target console's hardware, these big changes have in turn caused compatibility problems that have limited its appeal and lengthened its development. For less demanding consoles like Megadrive, GBA and SNES an interpreter is generally sufficient which can be ported directly from another platform, maintaining the high games compatibility derived from years of development of their parent x86 emulator.
In my opinion the implications of this is that most seasoned Windows Phone developers are unwilling or unable to undertake the huge commitment in writing an emulator which needs more advanced techniques than interpretation (which can be fairly easily ported from other platforms). Meanwhile developers of emulators on other platforms know that DynaRec is not available on Windows Phone, so either assume that a port is not possible (which isn't true in many cases) or would not be economic in terms of the work required versus the returns from the much smaller market.
In any case, I think you stand a much greater chance of progress if you seek out developers of existing Android and x86 emulators and ask them what it would take for them to port to Windows Phone. If they try to point out that it isn't technically possible, you should hold up EmiPSX as an example of an emulator (written by just one guy!) that proves fifth generation consoles can be emulated on Windows Phone and that methods other than DynaRec do exist (even if they'll never be as fast).