DataSource should be more feature rich. I consider following features a must in order to be able to develop complex UI's without the current pain

- Multimple models definition
- Associations between models
   - BelongsTo
   - HasMany
- Lazy load of associations!
- Allow use a REST approach for associations (send updates over a HasMany association to a service)
- Allow send the complete object

- Association validations
   - Unique
   - Exists
   - Min/Max number of elements