Is there a way to have an Expense Approver approve certain lines of a submitted expense sheet? That way the approved amount can be reimbursed in payroll without holding that processing back waiting for the employee to actually remove the lines that are not going to be approved.
A few years ago we had the same issue. The problem is that the expense sheet acts as a whole, regardless the projects you have. If one project manager rejects his expense entries, the whole expense sheet is rejected and able to be edited.
Our workaround was to tell everyone to include only one project in each expense sheet.