Maybe one more idea.
Instead of the ADI-642 for €2199 you could use the Octamic XTC for €1949 which also has 4x AES I/O via break-out cable.
The breakout cable is available as 1, 3 or 5m cable, e.g. this one for €65:
Like with the ADI-642 you can pick 8 channels out of the MADI stream and route it to the AES outputs.
The use of a breakout cable should be no issue, as this is digital transfer and such AES cables are designed for even much higher distances and you are also using a breakout cable at the DDRC-88D.
For even a little less money you would get on top:
eight very good mic inputs which can be used as line inputs as well (switchable: 4 x PAD, 4 x Hi-Z)
two headphones outputs
ADAT I/O (2x S/MUX)
graphical colour display allows for more comfortably configuration
And maybe also interesting as an additional use case (at least possible):
It's incredible how versatile the XTC is.
X10SRi-F, E5-1650v4, Win10Pro21H2, Cub11Pro, UFX+, XTC, 12Mic, ADI-2 Pro FS R BE, RayDAT