The Ancient Egyptians were also like us in that they were into architectural bling and greenery, so I'm not actually sure they'd be complaining that much. They were into materials like gold, electrum, and polished stone, but I'm sure you could sell them on modern glass.
That said, the Great Pyramid is a historical site, not an active worship site, and modern archeological sensibilities prioritise conservation. A restoration like that might make it hard to answer future questions about the pyramid.
I’m not worried about offending the ghosts of the ancients. Let’s try another analogy: if the Mona Lisa were damaged, should we “improve” it with “modern bling”?
That said, the Great Pyramid is a historical site, not an active worship site, and modern archeological sensibilities prioritise conservation. A restoration like that might make it hard to answer future questions about the pyramid.