The way I understand it, a replacement for Minimongo just for reading data needs two things:

  1. A simple filtering/querying API (doesn't need to be as fancy as Mongo)
  2. Change events on filtered views of data so that you can update the view
  when new data comes from a subscription

If you also want Meteor Method-style optimistic UI, then you need:

  1. Tracking of temporary changes from a specific method
  2. Ability to roll back those changes when DDP tells you it's done

Having a mongo-specific syntax isn't crucial, I think.