Restrict courier services by channel

The problem
Amazon Seller Fulfilled Prime orders must ship on Amazon Buy Shipping labels. However, Mintsoft still lets users generate a label from an external courier account on these orders.

When a Buy Shipping label fails to generate, it's easy for the wrong service to be picked instead. For example, our own Evri account services gets selected rather than the Amazon Buy Shipping Evri service. This has happened repeatedly in our warehouse. It puts our clients' Prime status at risk and affects their Amazon performance metrics.

Current workaround and why it doesn't work
Courier services can currently be excluded at client level. However, many clients sell on more than one channel. A client may need Evri for their Shopify or manual orders, but must never use it on Amazon orders.

The request
Please add the option to exclude or restrict courier services by channel, for example to allow only Amazon Buy Shipping services on Amazon orders. Restricted services wouldn't be selectable for that channel's orders.