The A119 comes closest to being IFR approvable - I believe all it needs is a second source of electricity (and that can be added to the transmission if memory serves me right).
The engine is basically the same one that is used in the Caravan and Pilatus PC-12 - both of which are allowed to fly IFR with paying passengers in N. America. The logic (and proof) was that this engine, under specific maintenance and operating procedures was much safer than the twin piston engine airplanes that were allowed to fly IFR. I wonder when the Europeans will see the light on this.