KI's HD image is 125MB and the ROMs are only 5MB. When loaded the ROM take about 18MB so I don't see any problems making this work on the XBOX. The HD image is basically the FMV so its not a problem.
The source has been available for a long time, but only 3.02 - RCP never release 3.05. I don't see this as much of an issue though, since the changes are not that significant. There are some problems with the FMV speed and the sound corrupts occasionally, but overall its a good emulator.
Also note that the u64emu will run on a PII 400Mhz just as well as it runs on a P4 1.6Ghz