I'd like to see Greg Egan's Orthogonal trilogy adapted into an anime.
The setting is a universe with an alternate law of physics whose consequences include that
¥ light of different colours travels at different speeds and there is no maximum speed of light
¥ liquids largely don't exist as a state of matter, they're all explosively unstable
¥ temperature acts weirdly (I didn't quite understand it from the books and Greg's website but it seems like the characters use gases as a way to dump arbitrarily high amounts of heat energy from their bodies)
¥ the direction of the arrow of time is determined by local conditions (entropy I guess) and in the greater 4-dimensional universe, the worldlines of objects can go in any direction. You can be hit by a tiny meteorite whose worldline is perpendicular to yours, which you will experience as something traveling infinitely fast, punching a great hole through your stuff and massively damaging it
¥ related to the above, it's possible for time-reversed matter to interact with ordinary matter and both see time running backwards (e.g. objects reforming from a broken state) for the other
and more.

The consequence of the alternate physics most important to the plot is that it is possible for a spacecraft to accelerate away from a planet so that it is travelling infinitely fast, i.e. 'sideways' in 4D space relative to that planet, then turn around and return, such that a short time passes for the planet's inhabitants but many generations pass on the spacecraft. (In our universe, it's the other way around, a lot of time can pass for Earth but the spacecraft ages less)
The plot is a multi-generational drama centered on precisely such a spacecraft, which the inhabitants of the planet built to buy time against a world-ending catastrophe.

Now, a problem I have with Greg Egan's books is that I never really like the characters, I'm only there for the math and physics. The characters tend to be annoying, unlikeable 'Young Adult protagonist' snarkers, and I never care about their stupid emotional problems. The plots mostly aren't interesting to me (Orthogonal's plot is one of his better ones, he successfully portrays the epic scope of the mission). When it comes to religion and woo, the author has the attitude and zeal of a reddit atheist transplanted from the 00s and so he'll write about a Victorian-analogue society inhabited by people who have never so much as thought about religion (because the author has resolved to never include religion in his stories), not that this stops them from being backwards and unenlightened relative to the protagonist who fucking loves science. Which brings me to the point about adapting it to an anime. In the anime adaptation, you could improve the characters by cutting the YA snarkiness and replacing it with anime earnestness. And after making that fix, please make all the female characters oppai loli mini giantesses (Pic semi-related. Females in the setting are already canonically larger than the males, the species has important differences from humans and Earth life in general. IIRC there is a scene where a female chases down a male and pins him, wanting to be bred by him, and that is where the idea entered my mind and would not leave.) The setting is one that would bring a lot of eye candy to the screen, with its multicoloured star trails, explosions, glowing rainbow plants, spaceships, relativistic effects and so on.