That's unfinished by the way, just to give an idea of what the structure looks like. Still need to get to a yes/no reject stage

The big problem is everything will be “hardcoded”. You can’t do a lookup of all employees by their department and approval level from within a workflow. So you would end up needing to put fields on the department record to hold the +$5000 Approver, +$10000 Approver, etc Or just hardcode it into the conditions

Trouble is the organization has been using suiteapprovals to do this and have no appetite for changing the requirement (If PO falls into this Dept and amount total above or below X, then Y approves otherwise M approves and so forth) It's going to be a weird workflow and like you say not easy to maintain