They wouldn't give you the same ride height. The spring with the double free length and half the rate is always going to be twice the length of the other, at a given load.
Take a 24" 100 pound spring and a 12" 200 pound spring, and put 1000 pounds on each of them. The 100lb/in spring compresses 10" and the 200lb/in spring compresses 5". The 100lb/in spring is 14" installed and the 200lb/in spring is 7" installed. This 1:2 length relationship holds regardless of load.
To continue with your example you'd want the 200lb spring to be about 80% the free length of the 100lb spring to produce the same ride height with a 1000 pound load. But if that load changes, it falls apart. Less load and the softer spring will be taller, more load and the stiffer spring will be taller.
yes, the 24" spring will have less uptravel due to coil bind, and the 19" spring will have less downtravel because the spring will fall out of the buckets. Push the rates far enough apart and you have two springs that wouldn't be usable on the same vehicle because the travel ranges wouldn't overlap enough. And because of having to stay within rates that provide a travel range useful for the vehicle it's being applied to, the influence of spring rate, within the usable range of rates, over small, or any suspension events is so miniscule when compared to the influence of the shock that the springs contribution is imperceptible to the driver.