I think as long as you use something very sturdy to keep the bottom from sagging it would be fine. I'd use a piece of masonite, paneling or thin plywood with rounded off corners if it were me. I'd also make some pockets inside and out for supplies. I've used pre-quilted fabric for totes and carriers with great success. You can go as fancy or as plain as you like. Personally I like to make at least one pocket large enough for magazines or notebooks for patterns, some for my cutters, cutting mats, rulers, etc. You might want one that has some form of gussetted bottom for the foot pedal and cord. Just remember, it's not rocket science--regular people have been designing these things for years. Take the time to decide exactly what you want it to hold and make your pattern to suit yourself.
ps: I would also use the handle strapping all the way underneath for added strength.