I've played this game and have logged over 300 hours on all difficulties including the infamous Lunatic+ Classic run. I would be interested in speed running the game on a more difficult level. Is there a chance that this group would add a Lunatic Classic section to this game?

There is no "easy" difficulty, Normal is the easiest difficulty.

I think a Hard speedrun is definitely possible and obviously will take more actions (therefore time) than a normal run.

Lunatic... I honestly wouldn't try. I assume it is still possible once female Robin gets going, though you probably want to pass Galeforce to Lucina and maybe get Morgan (I think it's worth doing his map just to make the rest of the game much easier and faster). TBH I'd rather do a Low Turn Count run if playing Lunatic, that sounds like more fun. But I don't think this is the site for those.

Hey, I actually found a Hard speedrun in segments. It's not a good runner by any means, and he did get very lucky with some level ups and that Anna shop with a Second Seal, but it proves it's possible to speedrun it in Hard:

I have been looking but have not found a Lunatic Classic speedrun. I'd be curious to see if it is possible; I imagine it is the exact same strategy as earlier difficulties (Chrobin solo + children) but much longer on average.

But anyway, I agree with OP and think it would be great to add a section for Hard and Lunatic. I'd be down to try a Hard run myself.

There are Lunatic+ "speedruns", don't know exactly how optimized they are, but it's possible to very consistently beat Lunatic+ without resetting. The main problems with it would be the long run times and the sheer amount of on-the-fly routing involved likely pushing away most people. Not sure how much the time could be improved.

This is a playlist rather than a single video, and later runs get the time to around 8 hours and change.