You should be able to set a general start and end target date for the project. Then it set some high level KPIs with due dates.
Then the graph view can show a timeline with that information as well as the specific "tasks".
Agreed. I frequently need the ability to break a smallish task into chunks and end up using multiple tools to do the job that would be really helpful if planner did it automatically.
IMHO I could see milestones implemented almost like a checkbox - you add milestones to a task and visually it lists those milestones with their dates and those milestones show up in the calendar view as well.