>where it's better to have one piece of technology that can comfortably cover a lot of tasks
As the old adage holds, anyone that is doing more than one thing is doing those things poorly. Trying to force individual systems to primary in more than one field is going to be difficult if not impossible - when these things happen in reality it is often more by fluke than by design.
Certainly, a system can have (often many) secondary roles as the system gets larger, but they must be designed around a specific role and designed to act in that specific role primarily, any and all other roles must take a back seat to that primary role. Otherwise, you end up with F-35s that can't do anything, as >>18493
Of course, over-specialization
at large scale is more deadly than under-specialization, just ask the Germans, but that's an aside.
To put it in a historical perspective from another field, the Sherman's 75mm gun was an excellent generalist tank gun but was completely outclassed in the AT role by the 76mm gun and the Support role by the 105mm guns. The US eventually replaced the 75mm gun with the 76mm/90mm specialist AT guns, even though both of them were terrible at the Support role, while bringing in more 105mm/155mm arty to supplement and eventually replace the Assault Guns. Specialization won out over generalization during the war
despite the Sherman being one of the best generalist tanks of the war and tank-on-tank engagements being the exception rather than the norm for the US.
That being said, logistics is a valid issue. It's a sliding scale of ease of logistics and system ability to do the job that can be hard to balance.
Admittedly, it does become a little ridiculous if only one ship or even a small handful of ships in the entire fleet use one munition that is meant to be fired in bulk, such as the Zumwalt's Unicorn 155mm shells, conversely this doesn't affect terror (excuse me, shock and awe
) munitions such as 16in or larger shells as with their limited role a unicorn status is expected. Any caliber change or introduction would have to either be handled fleet-wide (such as a return to the KK/FF/DD/CL/CA/CB/CC/BB system) or have commonality with another branch's munitions (such as the US Navy adopting a navalized version of the US Army's 155mm long-barrel gun).
>Can you see them entirely displacing autocannons, or at least to the point that the latter are just a backup in case the enemy manages to develop some unexpected technology?
Yes, with the caveat that it depends on continued investment. I believe they actually could displace SRMs on conventional ships and even supplement MRMs on nuke ships - this using extant technology. Although to some degree autocannons will remain regardless since invisible lasers are not a good threatening weapon against pirates or cocky civilians.
>Akhshually, what I have in mind is more like the South African G7 howitzer
Strelok, the G7 is still a 105mm Howitzer, regardless of how revolutionary it purports to be.
But getting to the point, bagged charges in rapid-fire guns are inherently more at-risk of causing spontaneous life changing events for the entirety of the ship's crew. If you're trying to reach several dozen rounds per minute, given the pure mechanical energy impacting these by-nature highly-volatile substances, this risk is exaggerated exponentially and makes your chances of a severe case of 'rapid onset ship disappearance syndrome' occurring reach near to 100%.
Obviously, caseless small-arms exist, but they don't push 12lbs of powder around at those speeds, and you can't be suggesting taking enlarged kraut space magic clockwork guns to sea; but I digress.
With larger systems where rate of fire is not really a concern, say 12 rounds per minute or less, then bagged charges really aren't that much of a concern so long as appropriate safety guidelines are adhered to religiously (in other words, good luck getting modern youths to abide by this); especially if you are using rigid foam body charges, which lets the charges safely be rough-handled a bit. This is because the charges can be stored in multiple layers of protection and only withdrawn when needed, much as they were in old bag-guns in WW2.
>But for an other alternative, how would 57mm guns work for CIWS?
be used in that role, fairly easily in fact. It's too small for something like DART, though, so you'd be reliant on your raw fire rate, but in practical terms it'd be a sidegrade to systems such as Leonardo's various 30mm/82s and 40mm/70s, all of which (including the 57mm) being sidegrades to Phalanx and the AK-630s. Superior in roles such as Anti-FAC, inferior in roles of Anti-Missile Defense, while being just as good against Drones and other larger, slower aircraft.
>theoretical 57mm guns and 57mm/105mm systems
I see no particular reason why they couldn't work
, but seriously at that point you ought to be considering upgunning to 3in/76mm and 5in or 130mm, or just sticking with the auto-cannons and running 5in/130mm guns out of weight concerns.