Currently there is the the option to calculate percent complete of a project based upon:
Planned Hours and Duration
I would also like the option to calculate the project's completion based upon the quantity of tasks incomplete compared to the quantity of tasks complete, whilst taking into account the percentage complete of the incomplete tasks.
For example, If a project had 100 tasks and 25 of them were 100% complete and 25 of them were 50% complete and the rest were 0% complete, the project would be 37.5% complete.
I would think you would have to ignore any tasks that had a subtask in the calculation.