<Snipped quote by Stern Algorithm>
The cool thing about gundam as an example is that they've been all over the spectrum between real and super robo, so you can kind of point at different places in the franchise for inspiration.
Like, maybe starting with something like Alaya-Vinjana, or psycommu controls; it's mostly a real robot, the thing that makes it special is how it integrates with the pilot, either psychically or perhaps through neural implants. Or maybe spiritually, if we wanna go that direction.
Then develop a "psycho frame" version, that's more integrated and lets the user project some amount of psychic power(or spiritual, or whatever!) through the robot.
And eventually end up with stuff that may as well be magic, like the GN particles in 00. They don't even pretend to explain the technology, GN particles just do whatever it is they need to. They're propulsion, letting the gundam just kind of float around instead of needing thrusters. It produces a field that can absorb attacks, and it can be projected into beam attacks. But also it fundamentally alters the pilots, and makes them evolve at a crazy rate(but there's also a "bad" version of the particles, that will cause DNA damage, but that's okay because the "good" GN particles can heal the damage too).
And if you wanna do combiners, maybe they literally just fuse together at that point. Go full super robo and just have a scientist do some techno babble on the side about how their constituent molecules harmonized briefly to allow the fusion, or something.
OK, this is a good idea. Instead of flying through space unassisted, the Ultraman-like character has a gigantic spaceship that they used to travel to Earth. Much of mankind's recent technological advancements were made thanks to reverse-engineering this technology, so it stands to reason that the core of the mecha has this black box AI that no one really fully understands. I will elaborate more on the lore in the actual RP thread once I've written it up.