Well, everything happens, even late...
"My apologies for the delay here, due to an influx with support tickets we are quite backlogged at the moment.
At present moment this configuration is not possible, though this may change with the addition of a monitoring mission coming to the MT48. As of now the MT48 operates as a mixer with four independent stereo mixes based on each output pairs.
In the case of the Neumann KH750 sub, the interface's main output (1-2) is wired directly to the sub, which then outputs to the satellite monitors. The sub is the intermediary between the monitors and the audio interface outputs. That may be an option to consider.
Neumann Customer Support"
Yes sorry, my post above was not clear.
Everything I mentioned above works with Monitor Mission which is only on MT-48's sibling product.
Until Monitor Mission comes to MT-48, will not be working.
Its nice that they confirmed Monitor Mission is coming though.