Provide option to calculate Project Progress based on time

We have many projects that have tasks with varying time estimates to complete the task.  I'd like to see project progress based on time, not completed tasks.  Let me give you an example. 

Project X has total estimated time to compete = 15 hrs.   There are 10 tasks. Nine of them estimated at 30 min each to complete (total 4.5 hrs) and 1 task estimated to take 10.5 hrs to complete.  Let's say the 9 half hour tasks are done. The current way TR calculates progress would show the project at 90% completed with in reality there's still 70% of the project left (in terms of time).  I'd like to have the option to calculate Progress based on time so I can see the project at 30% completed, not 90%. This would be a million times more useful to us.  Thanks!