Can we create an app on shopify app store and charge customers a monthly fee of 0.05% of their monthly revenue?
As far as I can see you could request information about the stores transactions to calculate the monthly revenue:
And using billing with additional use cases - create a add-on with specific price based on calculations made.
https://shopify.dev/docs/apps/billing/subscriptions/additional-use-cases
https://shopify.dev/docs/api/admin-graphql/2024-01/mutations/appSubscriptionCreate#examples-Create_a_subscription_with_add_on_modules