To make something able to handle higher g forces you must make it heavier, if it is heavier you require more fuel and launch power to get it to orbit. Mass drivers for orbit are of fairly dubious utility, especially for all but very compact very dense payloads. Being higher altitude at launch is of even more dubious utility for rocket launches, very little of a rockets energy is spent gaining altitude against gravity, as all fuel used fighting gravity is wasted. The bulk of a rockets thrust is used accelerating the rocket to orbital velocity. Even airplane launched rockets see limited use. For reference, the delta v (a measurement of how much a rocket can change the velocity of its payload) budget for low earth orbit is generally 9,300 to 10,000 m/s, the orbital velocity there is about 7,800 m/s. We’re talking about a fairly small fraction of a rockets ability saved before we figure in the expense and risk with making your payload and stages so much stronger and risking your delicate and typically much more expensive than the rocket payload with a much more physically violent launch. And the first chunk of a rocket launch is when you burn off a ton of the fuel while the rocket doesn’t get that much lighter relatively speaking, you’re mostly paying for fuel at that part of the process, and the fuel is far and away the cheapest part of a rocket.
To make something able to handle higher g forces you must make it heavier, if it is heavier you require more fuel and launch power to get it to orbit. Mass drivers for orbit are of fairly dubious utility, especially for all but very compact very dense payloads. Being higher altitude at launch is of even more dubious utility for rocket launches, very little of a rockets energy is spent gaining altitude against gravity, as all fuel used fighting gravity is wasted. The bulk of a rockets thrust is used accelerating the rocket to orbital velocity. Even airplane launched rockets see limited use. For reference, the delta v (a measurement of how much a rocket can change the velocity of its payload) budget for low earth orbit is generally 9,300 to 10,000 m/s, the orbital velocity there is about 7,800 m/s. We’re talking about a fairly small fraction of a rockets ability saved before we figure in the expense and risk with making your payload and stages so much stronger and risking your delicate and typically much more expensive than the rocket payload with a much more physically violent launch. And the first chunk of a rocket launch is when you burn off a ton of the fuel while the rocket doesn’t get that much lighter relatively speaking, you’re mostly paying for fuel at that part of the process, and the fuel is far and away the cheapest part of a rocket.