Vacuum tube materials

Could a vacuum tube (solely for audio use) be substantially improved with different than commonly used materials or even geometries, or have these things been optimized by now?
I have read of gold-plated grids being preferable.

For the cathode, what properties besides low work function are crucial for performance? Since it’s the cathode’s surface whose work function matters, wouldn’t we want the least resistive base metal still? What makes for an optimal anode material? Would a silver or gold (plated) anode offer any meaningful benefit over a nickel one?
Could it be that the differences between standard metals used and ideal ones might not matter so much in a preamp tube but actually might in a power tube?

Also, could quasimetallic NDD (nitrogen-doped diamond w/ high N content) be used as a coating for very hot -running cathodes, as it’s extremely robust and has a 3.1 eV work function?
Lastly, the Sennheiser HE-1 got me thinking, surely they aren’t the only ones using quartz tubes for nulling microphony? It’s a great idea.

I think the pinnacle of valve development occurred by the end of the 60s or 70s.

My depth in elemental chemistry isn’t too strong.

Most of those that designed these gems are long since dead as are many of the people it required to craft them. The demand cleared up in the 70s where I grew up. I saw the tube displays in grocery stores as a small kid but not past ~1975.

Hypothetically, could a better tube be built. I’m 100% confident it could. New exotic alloys and tune away. Unfortunately my fearless forecast of it ever happening is 0%.

It seems there is a place for a boutique makers. Some of the brands from China are probably pretty close to boutique. But the word gets out over time and they scale up and perhaps quality goes down.

Know of any tube craftspeople? Audiophile glass blower married to a metallurgist?