Yes, indeed, there is an item in progress that will deliver most, if not all, of this:
It will turn the collection into a ‘relation view’ with support for filtering/sorting/colouring, as well as hierarchical lists (showing levels below the first level of the relationship).
I wouldn’t say that it would allow ‘arbitrary queries’ but it will certainly allow a lot more functionality than is currently possible.
Yes, though to be clear, since @rawkode mentioned RoamResearch, Fibery doesn’t do that sort of in-line arbitrary query and filtering thing. But if you can do what you want right now with any existing View (table, list, etc.) and the available Filtering, Sorting, etc., and you just want to be able to do that in an Entity, then yes you’ll be able to embed that into an Entity or really any Rich Text.