Here is an initial draft of the application I am going to build:
It will be an SPA. On the left I will place a tree control where one can select a data source. On the right I will place a grid control. Although Mongo collections can store documents of different types I guess most collections will contain documents of the same type so it makes sense to present them in grid format. When first displayed I will build grid based on fields found in the first document. Columns can be changed in Fields control (by clicking on hyperlink with the list of columns).
Cmd control is to display a MongoDB command used to get data.