Dev on Recharge

Hello,
I am looking for technical support to implement a specific conditional pricing logic in Shopify + Recharge, and I would like to explain the setup clearly before discussing scope and feasibility.
Context
Store: Shopify
Subscription system: Recharge
Business model: subscription-first (olive oil subscription)
I sell olive oil products that can be purchased:
    
•    One-time
    
•    Or via subscription (Recharge selling plans)
I want to offer an oil dispenser (huilier) as an upsell product.
Desired behavior (core requirement)
The dispenser has two Shopify variants:
    
•    Regular (full price)
    
•    Member (preferential price for subscribers)
The logic I need is:
If a subscription product (with a selling_plan) is present in the cart →
The dispenser must automatically be proposed at the Member price.
If no subscription product is in the cart →
The dispenser must not be proposed.
If a subscription is remove...