This will be … challenging: a low-power diode laser doesn’t have enough oomph, particularly on light- or blue-colored fabric, to tolerate many losses.
The key problem: maintaining sufficient flatness over that huge area, because a millimeter up or down will put the fabric out of focus. Z probing the entire platform for grid adjustment will definitely help, but that implies pulling the fabric flat against the platform, which will likely require running a vacuum through a perforated table.
The 700×500 mm honeycomb for my CO₂ laser has internal stiffening rods and is still floppy-flexible, so IMO your huge honeycomb must be attached to a flat sheet to prevent it from collapsing. Perhaps an integrated vacuum platform with the honeycomb atop perfboard atop stiffeners on an aluminum extrusion frame?
The distance from the top of the honeycomb to the bottom of the vacuum plenum should defocus the beam, but you could make the bottom from aluminum clad foam board:
It’s not going to be easy, but it’ll be fun to watch when it works!
Some previous discussions: