Orville, the H8000's more limited predecessor, was pretty much anything to anything. The H8000 has a few restrictions, mainly associated, as you observe, with the Main-in and Main out blocks.
But, it's not as bad as you think. There's no reason why in the above example you cannot connect all the dsp inputs, rather than just two. Equally, the Main-out block allows two inputs to eah channel, allowing the dsps to be run in parallel.
Similarly the FW, AES8 and ADAT in can be connected directly to FW, AES and ADAT out, without going through the dsps. The main restriction is that the Analog in and AES4 inputs can only connect to Main-in, while Main-out is hardwired to Analog and AES4 out.