You confuse me. All altimeters are air pressure based. Radio altimeters are only used for AGL, above ground level. GPS based altitude readings are used for auto-pilot based calculations. Barometric altitude reading are the gold standard.

You must have been flying in South America or such to have such high cabin pressures. You could not get an aircraft altimeter on a commercial flight with current TSA regulations without some kind of special waiver. Maybe a watch based altimeter would work. When an aircraft is going to land at high altitude, the cabin pressure will be allowed to rise to the landing airport altitude.

It is very rare to land at airports above 6,000 or 7,000 feet. Aspen airport is at 7,815 feet altitude. It is not uncommon for the density altitude to exceed 10,000 or even 11,000 feet at Aspen airport. At such density altitudes. Many aircraft can not safely take-off or land with only a 7000 foot runway. Altitude effects the wings and engines of aircraft the same as it does brain cells. Too much altitude means too little performance.

Also, as I said, there is a big difference between muscle function and brain cell function. Higher level brain functions like judgment are seriously effected by altitude. This is no different than how alcohol reduces the supply of oxygen to the brain. Both effect judgment skills. Add altitude to PCS limitations and judgment can go downhill fast.