It should fit. Remember that the engine in the F10 550i is basically the same engine as the F10 M5 but detuned so the diameter of the exhaust should be the same pipe wise as both are V8's. Changes are likely due cat back and muffler back on the M5 vs 550i. However since someone has already easily retrofitted the M5 mufflers into their 550i and used the OEM rear valence it should NOT be too easy to do the full system. Check around some more and I am sure you'll find a willing shop/tuner shop. Dealer will likely balk tho as if anything goes wrong they won't want the blame..however it does depend on your relationship with them tho. Good luck and keep us posted.
'12 F10 550i (Dinan Stage 5/Intercoolers, CF Intake, Brace, Shockware, H&R Springs, Eisenmann Race Exhaust, CF rear difuser, Giovanni "Lindo" Graphite 20")
'10 e71 X6 35iDrive SAV (Space Gray) - Gone
'06 e85 Z4 M Roadster (Black Metallic) -Gone
'08 e92 M3 coupe (Sparkling Graphite) -Gone