I have two ideas that I never quite finished creating.
1. A story that talks about an armored hero something like,
"The Rise of Armor"
Something like for x reason sacred weapons are given to the protagonist
Is armor even a weapon?
I never decided if the story would be isekai or not, I raised it as a non-isekai in my case, but maybe an isekai is easier to handle the armor from a leather armor with a pocket with a lot of space it improves until it reaches an armor Tony Stark level, one of the most important fights was the nanotechnological armor against the strongest general of the demon king, something even more epic than the fight against thanos I have in mind.
The armor works based on science fiction combined with magic so that you have the choice to put what you want and the use depends on the mana.
The other was an idea
(starts as overlord)
in a mmorpg, i waited for the server to close i was summoned as a priest, next to my holy temple, i was summoned as a high priest, next to others as a hero, i had my avatar summoned with church and class clothes divine.
It could be said that an OP character but based on Faith, and sacred powers granted by God, a Messiah, a herald of god on earth
Another one that I wanted to develop, (it is not ruled out yet), I really like popular science and therefore science, including mathematics and everything.
I wanted to create an isekai, with a magical system based on mathematical and physical principles,
It included time travel, fighting in ancient times against anti-magic beings, thanks to the "scientific" system, the protagonist was the only one who could harm the bodies of these beings,
There was immortality, A Sacred Staff of a magician of Technology superior to human.
prophecies.
The Demon King resented the protagonist for being the only one who was able to defeat him in ancient times.
It included an ending where the protagonist uses one last trick, since he cannot defeat humanity's greatest evil by conventional methods, he uses a kind of "Elemental Forces Deterrence on Particles" making the enemy shatter into Protons, Neutral, Electrons. and later in Quarzt, but this or it was for free the protagonist consumed his matter through E=mc2, and used the energy of each atomic nucleus of his body, and dies at the end of it all, saying goodbye to his friends and loved ones, turning into dust of stars