As the module library grows, a pricing decision is needed: include all modules in the Professional tier (simpler, higher baseline value, less friction for clients), or sell modules as add-ons (lower entry price, upsell opportunity, but adds billing complexity and may reduce audit completeness). A hybrid — core modules included, Module 5 RE and Module 3 Custom as add-ons — is a middle option. This decision directly affects the billing architecture (D-23) and the value proposition communicated to audit firms.