Fiori Timesheet approval app without workflow

Hello Friends,

One of the clients planning to go for Fiori app implementation and they are Timesheet entry & Timesheet Approval.

For Timesheet approval, they don't use workflow at all for the managers to approve subordinates timesheet. Instead, they use structural authorizations and use TCode "CAPP" to approve time sheets in ECC. They use both A002 & A012 relationships and Managers will approve time sheets for all employees in the org unit and subsequent org units.

My questions here is without workflow and just by using Structural authorizations will standard Fiori timesheet approval app will work?

Or

Do we need to go for custom app?

Please let me know your opinion.

Regards,

S.Srikanth