Lock timesheets and expenses to be separate

At the moment the lock on a sub project locks both timesheet submission and expense capture.

We would like to be able to lock timesheets for employees on a sub project but still be able to import expenses from Xero or capture an expense to it.

Or when a sub project is marked as a passthrough we would also still like to capture the actual expense cost against this sub project but block this from timesheet capture.