It isn't too much, but it mainly revolves around the fact that Spike is a demon while the Mane Six/Seven are angles. Main idea is, the girls are sent down to earth after being informed that a demon has arrived there and have to find and stop the demon from doing whatever devious plan it might have. But in reality, demon boy Spike only wants to hangout and relax.

7513765
Basically a case of he's done nothing wrong, but has to be taken care of because of the threat some feel he may possess

7513768
Pretty much, but their only drawback is that they to justify their actions. Let's just say after a misunderstanding that happened hundreds of years ago that almost led to earth being destroyed, they have to know for a fact that he's up to no good, otherwise they could risk the same thing happening again. Especially if they were to kill the son of Satan himself.

7513765
I think it'd make a good one shot, but not a mult-chapter story.

I would be really invested on reading a story like that