This would be an interesting project to do. I can't really say which audio would be the best, as I know there were tampering with it. Most releases contained an audio track different than the original (overdubbed lines, new sound effects etc.); the theatrical audio track may have been never released.

Back in the day, Hong Kong Legends made an effort to recreate the theatrical track for their DVD by using different sources. They've ended up an reasonable compromise. I don't know if a better audio for the Hong Kong version ever came. If the Japanese LD version is surely untampered with then fine.

As for the video quality, I've seen the Japanese Blu-ray, and it looks OK for an old movie. It's not super-sharp but much more detailed than a DVD. The colors are pretty dull. If I would do this project myself I'd take the luma levels and colors from the New Line laserdisc version (they look superb), and eliminate the burned-in subs with masks using other releases. Police Story could look awesome again.