I had one of the front clearance lights leak, fortunately a lot so I caught it right away. The hole for the wiring was large and offset high, so only a tiny sliver of butyl sealing it. I've had one of the vents, the shower skylight, and fridge vent leak too, resealed them.
I've also looked at replacing the Bigfoot with a custom that I would build myself, I'm thinking the budget for that is somewhere around $80-100K plus a year's work or so, probably not happening. Even then, you are stuck with RV appliances, windows, hatches, etc. which are built to a very competitive price and show it. Perfection is hard to achieve.