Lexus as a minor sub division of Toyota isn't going to get the funds to develop a special drivetrain for the CT. Toyota would need to develop the Auris and other models with that drivetrain which Lexus could then use - which is all they did with the current CT compared to the Auris Hybrid.
If TMC want to compete against Honda, SEAT, Ford etc then they would do so with a T badged vehicle, not one with an L.
There shouldn't be reliability issues, the Toyota/Yamaha 3S-GTE engine used on the Celica and MR2 turbos was absolutely bullet proof at the standard 240 bhp - Toyota know how to make a good turbo petrol engine.