Thanks Jakkson! Diesel-electric support will be coming eventually as soon as I get some other stuff out of the way first (the editors for instance). I'll need to research how it works in detail to model it to the same fidelity as the mechanical and hydraulic transmissions. The train editor will allow the community to add the classes you mentioned while I focus on developing the core sim.
It's true that the diesel-electrics share a lot of similarities with purely electric locos but I don't yet know to what extent. There might be some differences in the control mechanisms. The infrastructure is also a major point, not just in the 3D-modelling of the power rails or overhead electric lines, but because of how multiple electric trains drawing current from the same transformer affect each other's performance, unlike steam or diesel locos which are independent of each other.