I don't know the precise terms. In FM synthesis, you use two 'sounds' and magic happens, and I like to use FM synthesis for some of my sound design in the Virus.
But the routing options are too limited. I pretty much have only FM amount, and of course i can choose which wave i use, thats great. And very interesting results can be created.
However, I would like to see a further development of the FM synthesis part. Think modular FM, similar to FL studio's Toxic Biohazard software plugin, or NI's FM8 software synth. Basically, you can several basic waves (Sine, Triangle, Square, Saw...) and up to a total of say, 6 basic wave, then you would be able to use wave 1 to modulate wave 2, wave 4 to modulate wave 3, wave 3 to modulate wave 1, and so on. And imagine, you can also use LFOs to vary the results of each! This sort of thing for sound design, would be awesome to have, and its mostly applicable in Dubstep, or some other form of electronic music maybe? Once I got a little in depth with FM synthesis, I quickly realized the power of it for sound design. One hardware synth i know uses a more detailed FM synthesis is the Elektron Monomachine. Forget the fact that they have implemented SID emulation, but the FM+ 'machine' they have, is an example of the kind of FM synthesis that is useful and just opens up more options.
As someone who like to make their 'samples' or 'patches' from zero, this could be a considerable addition to the already powerful hardware. The issue is not hardware, its just the OS implementation. This could be one way of doing it, I have say 4 parts active with certain waves I have used (basic or wavetables, etc), then for FM sound i could have access to the other parts sound, and vice versa, like part 1's say sine wave could affect part 4's square wave, and part 3's wavetable wave, could also affect part 1's sine wave, with some of the parts' output / patch volume or whatever muted, and so on. See picture below for an idea of how it can look like.
[Blockierte Grafik: http://www.image-line.com/extimages/ToxicBiohazard-fullSize.jpg]
or that one
[Blockierte Grafik: http://www.creatingtrance.com/wp-content/uploads/2012/10/How-to-Make-a-Filtered-Prog-Trance-Saw-Lead-with-FM8.png]