you absolutely can make actual all-terrain vehicles like, you can have the same vessel able to navigate land, water, underwater, air, and space but getting all of that set up properly, not to mention the sheer amount of resources it will need to carry on board for the engines that need to lift enormous weight, and then also guns and stuff, it's really time consuming to design, and also gonna cost you an absurd amount of materials It's really preferable to make specialized vehicles that have particular tasks and roles in and out of combat like, an orbital laser is a great thing to make, even if it's a bit wonky to get it working, and "space" is only 2km up in the air so it will need some defensive capabilities or a handful of missiles will put it down real quick but if you try to make a battleship that can also be an orbital laser, the cost and complexity balloons
the next thing I wanna make is a spy sattellite cause fog of war is a pain in the ass, so it'd be handy to have some relatively cheap little guys I can just shunt into space and get some vision then I'll get working on something that can actually fight, probably just a glorified container ship with a buncha missiles. They're expensive in use, but really effective and easy to set up and if you launch enough of them, point defense hardly matters if you can shoot down a missile a second, I just need to launch enough that there's more missiles than seconds until impact once they're in range Really it might be beneficial to have multiple, slightly cheaper ships with a handful of missiles each, rather than one big boy with a ton cause like, if I have one Large Lad, that's a single point of failure, it's one unit that can be targeted and if it's hit, the battle is over
