[dcb]

If you have to brake, hydraulic looks like a good option.

For xmitting power from the engine, there are still many situations where direct drive, and neutral drive, from the engine is substantially better, IMHO.

Though perhaps a hydraulic transformer would be a good fit for a downstream Rankine cycle application, as that will need some "impedance matching" almost constantly, and the series losses will be less (assuming the power recovery from the downstream Rankine cycle is less than the engine)