Although I'm not quite convinced that you can sel the B350 as a 9 seater aircraft (AFM says max seating is 15) and the OM has to be approved by the CAA, so f they don't approve the OM that's it. The problem is that the B350 is a bit of a grey area. It's not a part 23 aircraft (under 5700 kg) it's not a part 25 aircraft (over 5700 Kg) it's a part 23 aircraft over 5700 Kg).
I think basically what they meant here is performance class A aeroplanes
Performance class A aeroplanes’ means multi-engined aeroplanes powered by turbo-propeller engines with an MOPSC of more than nine or a maximum take-off mass exceeding 5 700 kg, and all multi-engined turbo-jet powered aeroplanes.
As far as your dash-8 plan goes this won't work because in the beginning of ORO.FC.100 Composition of flight crew, it says:
The composition of the flight crew and the number of flight crew members at designated crew stations shall be not less than the minimum specified in the aircraft flight manual or operating limitations prescribed for the aircraft.
And I'm sure it says 2 pilots in the AFM.
But if your local CAA will approve a B350 with 9 seats single pilot, by all means go for it.
Having flown both the B350 and the CJ series I rather fly single pilot in a CJ (multi engine turbo jet powered aeroplanes) than a B350 but according to EASA this is difficult and definitely not allowed. So much for smart rules and regulations ��