A few things here:
It would be really nice if the front-end user had the ability to engage with dynamic data, like filtering options eg for blog posts set it from old to new or visa versa.
Smart data paths for collections would be nice, like https://www.typeform.com/ does in their forms,
this way when a collaborator is given a certain option the next options will depend on his previous answers, eg I'm adding a new item to the collection "Clients" and I need to fill in if the client is a business or person, if I choose Business I'll have to fill in VAT and such.. if It's a person I would not get to see those options..
I hope I'm being clear here
The ability to simply duplicate items in a collection, when you're working with complex data structures it would be really easy if we could just duplicate them..