A larger issue here is the very idea of different armed services. If you were designing a military today, would you have Army and Marines? I don't see how it makes sense.
Let's fast-forward a few decades. If we have combat robots (not that I'm advocating this, but I think that's where we'll end up) then brain-wise one soldier can know everything that another can. I.e. there's no need for different MOS. You can have one brain that is both a special-operations infantry assaulter, and knows how to service any aircraft in your arsenal. The real differentiator would be morphology of the units.
So, if every unit could conceivably be trained in all tactics and doctrine, what's the point of services vs. just specialities?
Division of labor, and producing specialized units.
Marines are traditionally a power force to be employed from the sea (amphibious) while the army is mostly land-based operations. Do they both see armed combat? Yes, but they are specialized for different scenarios.
If we had a robot armed force, would it be better to have a single, mass-produced ubiquitous unit? Probably not. There you would probably want robots designed and specialized for each of their combat scenarios.
Let's fast-forward a few decades. If we have combat robots (not that I'm advocating this, but I think that's where we'll end up) then brain-wise one soldier can know everything that another can. I.e. there's no need for different MOS. You can have one brain that is both a special-operations infantry assaulter, and knows how to service any aircraft in your arsenal. The real differentiator would be morphology of the units.
So, if every unit could conceivably be trained in all tactics and doctrine, what's the point of services vs. just specialities?