If would be great if when adding a subgrid to a form if you had the ability to select which Form would be used when opening records from within that subgrid.
You could have an Account record with 3 different subgrids all pointing to the Contact entity, but showing different views based on (filtered on) Contact type.
If you also had three different forms created for the Contact entity, each showing different fields based on Contact type, it would be nice to show a different form for each subgrid.
I know this can be done using business rules to show/hide fields based on the value of another field but sometimes these business rules can get very lengthy where it's easier just to create a different form.
(this would be similar to the functionality on the portal but available in the web app)