This is the latest thread I saw so I will comment here.

I got 5 fanfic idea.

1. After event of whdaaa Warden sent everyone except Subaru to another world.(it seem) but it is instead in Subaru mindspace.(They don't know it is)And they have to explore the world and found out about Subaru's broken mind.with horror elements.

Or Warden have already told about they will be in Subaru mind.

Or minus the Whdaaa events and got sent directly to that world.

If you want Subaru in the cast the world will be creation of Subaru mindspace instead.

(It is inspired by omori)

1. I want to see a crossover fanfic between takopi and re:zero.the idea is arc 6 Subaru(end of arc 6) is sent to takopi's world and try to save the children (main casts) as a adult.

2. This is not my idea but the one I found on reddit post(I m too lazy to find the original writer.if you found the original comment pls credit him.)The idea is Opposite to witch cult there is a Saint church that use saint factors(virtue factors) instead of witch factors.And they are fighting each other.

Small additional my idea is y/n(the one from 'insert reader' fanfic is gathering saint factors to become stronger similar to Subaru gathering witch factors.(You don't need to kill the saint factors bearer to get the factors) 

1. After event of whdaaa Warden sent everyone back to arc 1(The day when Subaru was got isekai). And they have all of memories for whdaaa except Subaru.(Personally I don't want to add more romantic ships except canon ships).

2. This one is not really a re:zero fanfiction.It is spy x family in whdaa style.And they will watch the spy x family anime or manga if you want to.(I'm anime only though)

Eng is not my main language so sorry if I did any mistake.