Capturing Import/BOE cost item wise

We want to create PO (Majorly imports) with taxes (BCD + IGST). Please let us know as how we can achieve the below

- We want BOE to be kept outside Oracle and would like to perform GRIN/Receipt without BOE. At the time of receipt we can remove the tax category or make it blank so that GRIN/receipt can be done without BOE. But how we can record item wise Custom Duty, IGST & other non-recoverable cost post receipt. In AP work bench we don't have provision to capture details item wise and further we don't want to enter each line manually.