[Maarten]

The chance of glass failing under normal circumstances is almost zero, so no additional measures need to be taken. The only real concern is that if it should fail, it fails as safely as possible.

Trinitron tubes use an aperture grille. While a shadow mask is a piece of sheet metal with etched holes, an aperture grille consists of wires under tension in a heavy steel frame. The wires are vertical, so they only limit the horizontal resolution. Compared to an etched mask, the grille is relatively coarse due to its heavy construction and the size of the wires, so Sony and later Mitsubishi, constantly struggled to keep up and it's an amazing feat that they kept up as long as they did, using what was initially an emergency solution to get a conventional variant on their originally planned more complicated colour tube to the market without paying license fees to RCA for using the shadow mask (which was probably their emergency plan C). A distinct advantage of the grille construction is that the area of the phosphor stripes that can be illuminated is larger than in a shadow mask system where the mask gets in the way.

I think it should be clear already, that you can't leave out the wires from the grille (there would be nothing left) to obtain an unlimited resolution in both directions. The best way to obtain a resolution as large as possible using conventional means would be a shadow mask with a cleverly designed dot pattern, since that gives the best compromise between horizontal and vertical resolution.