I foresee a problem complying with 25.903(b):
(b) Engine isolation. The powerplants must be arranged and isolated from each other to allow operation, in at least one configuration, so that the failure or malfunction of any engine, or of any system that can affect the engine, will not -
(1) Prevent the continued safe operation of the remaining engines; or
(2) Require immediate action by any
crewmember for continued safe operation.
With a single lever, how will you provide isolation for a failure or jam of that lever assembly?
It would also make intentional asymmetric thrust rather difficult (such as setting a malfunctioning engine at idle to provide electric and hydraulics, while actually flying the aircraft with the other)
As dixi notes, what problem are they trying to solve?