The desire for this sort of flexibility is a mistake. It sounds good, but it's naive. It's sort of like saying you want a single class in your OO design to be "

The desire for this sort of flexibility is a mistake. It sounds good, but it's naive. It's sort of like saying you want a single class in your OO design to be "flexible" so you make the class into an undifferentiated mess. Having a monolith class that "does it all" is a red flag of bad design. It's truly no different when the layer of abstraction is human software developers being organized for complex business problems. Having "flexible" people whose job is a little bit of everything is a major red flag of a bad design (bad management) that took the lazy way out instead of the harder but unequivocally more successful route of actually meaningfully dividing the workload between clean interfaces and having employees mostly specialize. "Sometimes you just need somebody to work across every system" is just flat out wrong. If you find you need that, it means you've been doing things in a very wrong way and patching over it by commanding positions to be full-stack is only going to perpetuate the problem.