If your solution wanted to avoid business activity on S-S maintenance then i suggest to leave it to ABAP team to determine the corresponding approver.
The workflow will be different for handling Travel and Leave approvals. So, they can manage based on your customer needs.
Here i recommend you to think about entire Org Hierarchy and their respective approval paths with your customer and get a confirmation on how the approval needs to happen for those all different scenarios, accordingly you finalise the solution to drive from ABAP team to avoid any future issues.
Thanks,
Narendra Katuri.