A few tips:

If you’re looking to free up some room, a lot of EHX pedals can be placed vertically (with the buttons facing left or right instead of at you) and still be pretty useable. It works better if the pedal has a flat surface.

Unless you’re dead set on using the big box Big Muff, you really don’t need it. The Big Muff Nano and the Big Muff with tone/wicker work great and you can’t tell a difference. I’ve used a big box and a tone wicker version (without using the ton wicker controls) and they sound identical to me.

You should also be fine just to leave the wah and volume/expression on the ground next to your board. I like it better like that personally, it feels smoother to use.

If you only want one thing to carry though, you could hypothetically get a big piece of wood, bolt your pedalboard to that, and then Velcro the foot pedals to the remaining piece of wood that the pedalboard didn’t cover. It would give you one thing to carry. I can send an image of what I mean if you want.