I used to do this as part of R&D efforts at my employer 15 years back. It was pretty dirt cheap to get someone to decap a package like this. You could also get

I used to do this as part of R&D efforts at my employer 15 years back. It was pretty dirt cheap to get someone to decap a package like this. You could also get them to put under an electron(x-ray?) microscope and fly around the chip like an airplane simulation. Then they would use something called FIB to cut and draw wires to test out bug fixes. Usually the designers would keep a couple unused gates at periodic intervals to borrow for fixes.