Confirm there are not already settings or features that do what the shop is asking for:

Confirmed. There is currently no built-in feature or setting that allows a shop to set a subscription without offering a discount. The system mandatorily requires a discount value between 1% and 99% when enabling subscription settings for a product.

What does the shop want the product to do?

The shop wants to create an exclusive subscription-only product without applying any discount (0% discount), selling it at its full regular price solely to recurring subscribers.

Why/how would it improve sales or efficiency?

Sales: It allows the shop to create exclusive, premium subscription offerings that drive recurring revenue without sacrificing profit margins through forced discounts.

Efficiency: It eliminates the workaround of artificially inflating retail prices just to offset the mandatory 1%–99% system discount, streamlining product setup and pricing management.