If you can absolutely guarantee that it’ll never be done wrongly, then sure. But that’s impossible. Yes of course there are some very few cases where it’s essentially indisputable but there’s always a line to be drawn somewhere and as soon as any judgement or room to wiggle comes in, it all goes wrong.
I’ve nothing against the concept frankly but it’s impossible to do perfectly and can’t be any less than perfect.
As for deterrant, nah. Deterrant effects don’t depend on severity of sentencing, except for low grade crimes and career criminals. If you’re not deterred by life you’re not deterred by death- you’re doing it either because you’re crazy, you expect to be caught and welcome it, or you don’t expect to be caught.