Selling 3 year Subscription along with a physical product

Our requirement is to capture order for a product along with 3 year subscription (upfront paid). Order acknowledgment to include both product and subscription.

Separate accounting for subscription order line, Segregation of product and subscription cost.

Partial shipments: invoiced only for the product shipped along with subscription line on the invoice.

Can you please let me know best practices to achieve it:

I have tried - Buy One, get one for subscription line (Bill Only) but it doesn't work for partial shipments.

Line Level - Charges for subscription but it is invoiced as a fixed inventory item used for freight at the invoice.