Electric tailrotor shouldn't be too much problem with current power generation and electric motor technologies. Plus electric motors are the most efficient means of mechanical drive. Besides the concept of electric drive in a conventional helicopter was proven last year....

HeliHub.com Electric R44 takes flight

W1

Brushless elctric engine on battery one story. Piston engine -> generator -> same electric engine, another

Speaking form development experience, of one aux PBS turboshaft running air compressor and AC genset.
Our luck, helicopter was big enough to sustain all extra weight penalty....

@500e
let's hope that some of PBS new turboshaft design can sustain (prohibitive) certification expenses. Mi SAFIR APUs from the same company are certified.

@onetrack
yes, but please read in which stages of flight and if we goes on Maryland side, than this can be useful reading too ->
http://drum.lib.umd.edu/bitstream/19...i-umd-5771.pdf

Any updates on this Diamond development? I wonder how this would play out against Guimbal's eventual 4 to 5 seater.

Last October the CEO stated in an interview by a local newspaper that it will have a turbine (+ the already known electric tail rotor/retractable landing gear) and that it will be finished around 2020-2021.
Two months later Diamond has been acquired by Wanfeng Aviation Industry - no idea what impact that has on the project.