The M5 wheels will not fit as the offsets are too low. Regarding xi wheels in general, BMW's upgraded sport 124 wheel is available in an xi-specific fitment with higher offsets. Check realoem.com for part #s; they differ from the rwd 124 wheel. While the xi's are awd, they are rwd-biased and there is no problem running a staggered setup. BMW's own upgraded tire/wheel package for the xi is staggered.
640i Gran Coupe | M Sport | Sapphire Black | Amaro Brown Merino (indiv) | Dark Red Sycamore (indiv) | Bang & Olufson
N54 535i xDrive | M Sport | Platinum Gray | Logic 7 | Nav | HD Audio | RDSport Roof Spoiler | Dinan Stage 2 | Dinan Exhaust | KW v3 Coilovers | Beyern Mesh | Conti DWS 255/40-285/35 | RPI Scoop | Gloss Black Kidneys | (sold)