Dennis @ PerfectForms
Your solution is viable, but the workflow will be fairly complex because if manager #2 gets there first you have to decide to which workflow stage the instance will route next. You will have to account for every scenario.
My preference is to have one manager approval stage. Create a condition that to move to the next workflow stage all four manager’s approve checkboxes (or radio buttons)must be checked. If any of the managers clicks reject and submits, route the instance to a rejected stage.
Use a different role for each manager. Send their notifications to their roles so that you can control the visibility of their approval groups based on their role and the workflow stage.