Wow, that one guy's cab is really cool, and looks good despite it having no paint/laminate/artwork/etc. I totally don't have the skill to do all those curves. I hadn't even entertained the thought of fiberglass either...and I won't. That's just way too involved for me...especially for a first project. I do like how he kept it open underneath, makes it easy to get close, and put your feet underneath it. Something I'll keep in mind.
As I said, my other thought was a tekken5 cab knockoff. I think they had a pic of it on klov. It used the least material. Metal lets, a trapezoidal box to hold the pcb with the coin box attached to the front, and a control panel attached underneath the monitor. It's very...skeletal, and I like that.
I also know a guy who knows a guy (wow) who runs his own arcade so I might be able to score something that's already made. So who knows.