I believe the Tangara's really need to get their motors changed so that they don't first start up too loud and also to raise efficiency. Mum doesn't like not only the lack of reversible seating on sets T1-T99, but also the high-pitched DC traction PWM sound when the train first starts. So I believe they should change the current Mitsubishi Electric GTO thyristor–4-quadrant choppers with 2-phase DC shunt-wound motors to Toshiba IGBT–VVVF inverters with permanent magnet synchronous motors, like those of the JR Kyūshū 305 series.
The second advantage of doing that is to also raise the efficiency of the traction motors; the VVVF inverter keeps your 3-phase AC or permanent magnet motor always efficient and delivers the DC motor-like instant torque much better than a DC motor (as you know).