Has anyone ever built your own case with all the custom nooks and crannies that you desire, and using a folding mat? I have a design in mind, and I guess that's all it really takes. That and some time and money. I'm wondering if anyone has experience and could clue me into any pitfalls that lay ahead.

The person building the item should have performing experience, on a regular basis. The needs of a casual performer are often very different than those of someone who performs regularly. Workers are the most qualified to design such an item.

I prefer to work out of a duffle bag, with cardboard compartments, sitting on a tray stand. I've yet to see something more practical than that, on the market, for the type of show that I perform. Those who perform large stage shows will have very different needs.