Luxuriant
the normal trend is always human reincarnates or is summoned to be a hero to defeat the demon lord, then he has to go through stupid trials only to be betrayed at the end. Those are generic. Tensura? It was perfect. This is just my rambling as a lover of the anime, manga, and novel. Take it however you like.
The deaths that made him learn his lesson. The demon lord evolution, Harvest festival. Business reform. Military reforms. All these made Tensura one of a kind. You can't see its kind anywhere else. 'A reincarnated human becoming a minster and then a demon lord and actually achieve peace with humans' Come on bro. Think about it.
Umm. Not to sound like the only odd ball out of everyone here, but I think the author should pay attention to some details. I know its a fanfiction, but some things shouldn't be changed. The little girl who came to blame Lucifer for killing her father was right. If he wasn't so cocky about everything nothing bad could've happened. We all know that throughout the original light novel, nobody died and remained dead in the tempest. So my honest opinion is that you are ruining the Tensura we love. Also, need I remind you that Rimuru is actually Veldanava's reincarnation with Great Sage/Raphael/Ciel being his wife, Lucia's reincarnation? Just saying. Don't take it as a bad comment. But if you really read the novel and actually understood it, you'd realize you're actually ruining it. The novel was perfect as it is. There were no tragic characters and no plot holes. It was perfect. So at least if you want to write a fanfiction on Tensura, take it way back as possible.