Hrm, I'm not sure sure it would be that easy to port the plugins, as the xbox won't let you dynamically link to any code. There's no such things as .dlls on the xbox - everything has to be statically linked into the executable - so you have to have the source code to have any chance of getting the plugin working. When I ported Daedalus, I had to re-merge the graphics plugin source back into the main codebase.
That said, if the plugin source is available, it's not too hard to do if you have a wrapper around the calls to the plugin, because you can just call the statically linked code directly. After that there's not really much work required to get DX8 code working with the Xbox (it's actually a lot simpler to create the render target and initialise everything, as there's no device enumeration to bother with). There's a few subtle changes that are needed - like you have to swizzle all the textures if you want to use the wrap or mirroring addressing modes, and that can be quite a performance hit.
There's no DirectInput, so input plugins need to be changed to use the controller api (which is a lot simpler than DirectInput anyway).
I've not got sound working in Daedalus-Xbox, so I can't really comment on that, although I guess it's not going to be that difficult. Having the source for an audio plugin would obviously help though.
StrmnNrmn