Say, you know what would be really cool? Sembalances are the result of one's personal "Dust Within", and while can be replicated, are extremely unique to one's existence. As everyone is made of chemical elements, extremely complex organic components, magical energy/Aura and Dust in Remnant, there is no one exact Sembalance, and one's soul that generates Aura is believed to attract the kind of Dust one has affinity with.
"Dust Within" even builds upon itself! Dust Within, while it doesn't make external use of Dust obsolete, is a kind of "vital body" mysticism and magical science that is studied, ESPECIALLY BY HUNTERS, to unlock their inner potential and allows them use of a limited predetermined set but ever growing series of spells/powers with training, repeated applied use and realization to ensure they are not fully powerless against monsters like GRIMM IF THEY ARE UNARMED OR CAUGHT BY SURPRISE. EVEN BETTER, WHAT SEPARATES THESE POWERS FROM SEMBLANCES are that Dust Within powers utilize basic function and even specified usage of Dust within one's self, where Semblances requires Dust Within to work fully in unity to be activated. Holy fucking shit, I just bridged and fixed your magic system guys! Even Monty's giving me a pat on the back!
This makes way for Hunters who are straight up mages/magic users or even more different fighters than the series' typical hybrid magic fighters! Fuck, Dust can even have the same life force mechanic as the Lifestream and Mako if you wanted it to, making for summoned monsters and shit!
Back to robots, while they aren't certainly useless, they aren't very thought out either. Maybe robots are a way of doing things without attracting Grimm. The point is that tools are build by men out of a need, not out of a cheap want. Maybe every Hunter Team could have a super mech in the case of them encountering gargantuan threat Grimm, and that could also act as their storehouse for their flying arsenals. The other elephant in the room is that unless there's some super technology on the par of Megaman, and even then, robots have their weaknesses too. Metal has a tendency to warp, corrode, and consistently degrade if left in even the smallest of affecting conditions. Wear and tear definitely is an issue. Electrical components and power supplies are also not infallible. Electronics and robotics are also stupidly intricate for them to work, else they turn useless. Current tech is also consumption heavy, and then you also have to worry about if your robots will become cancer stations. Gee, THIS also would need some sort of technological explanation. Even in big mecha and tech heavy anime series, there's always a mechanical designer who also gives input and helps to explain how their technology works differently than real life.
OH I KNOW Dust Tech is used to create a sort of "organics system" to humanoid or organism based robots, giving them an inorganic skeletal and muscular system that allows them to overcome the fragility and intricacy of more basic joint systems that can seize and be more easily interfered with outside ordinance. Basically it's like the psionic android tech in Star Trek TNG or even Aliens, but more applied. Also, when a user pilots it, they have to "harmonize" with the mecha, which allows them to control it with nothing but their own action but piloting it is exhausting and they can feel anything the mecha does. I could also probably see how giant mechas could be extremely useful in going to ruins where they are incredibly large scale made by giants relics, but would require a vast amount of time to scale for a human.
