Not, I think, on the X2... look, the GBA had a single 16MHz ARM chip, and one chip (iirc) that was for custom sprite accelleration. We got GBA at a playable rate, but ONLY because of the tricks used to essentially turn a GP32 CPU into a GBA CPU as opposed to run a virtual CPU on top (seeing as they were binary compatible). And even then, once the sprite hardware was emulated, it slowed down a LOT.
The X2, at best, is 2 and a half time the speed of the average overclocked GP32 (i.e. 166x2 is 332, half again is 415, the 15 MHz in addition seeming a perfectly reasonable rate of OC). The DS, in comparisson to the GBA is about 7 times the speed (well, one 66MHz ARM cpu, and one 37MHz one or so). It, in all liklihood, has some custom gfx hardware too. If that's the case, then there is absolutely no chance whatsoever nu-uh no way and even if there were it would not be playable.
Conceivably if it DOESN'T have anything but an Arm9 and an Arm7 chip then yes, it might be done, but do NOT get your hopes up until you've got a techdemo running at a good speed in your hands... the chances are astronomical imo, especially since you need an MMU to do CPU mimicing tricks, and only one of the ones available on the x2 has one (the 920t). Let alone that its hard to use it unless you bypass Linux which may or may not be completely straightforward for the average coder.