Ah, ok then. This is what I mentioned:
Return Stored Source Fields — MongoDB Atlas
This way index will store those fields and will return them immediately instead of returning the full documents to which these fields belong.
But it seems, either way, you will need subsequent matching stages on documents returned from index search stage: https://www.mongodb.com/docs/atlas/atlas-search/performance/index-performance/#storing-source-fields
What I meant is, by the way, even though the index works with accents differently, the returned documents from this stage should retain their accents on which you may have a match stage with collation.
PS: I am not 100% confident how stored fields works as I haven’t used them before. I just trust the documentation 
PS again: I might even be mostly wrong and this one might be what you need. please check on how this storing option works thoroughly.