How to use Container Functionality in Non WMS Organizaion

Hello

I am looking to implement the functionality where we want to use Containers for  all the items. Now, I am aware about creating Item Container Relationship and then Container will be automatically assigned to the delivery.

But in this business case, users want the flexibility to book the items in the boxes based on the requirement. For eg - If they have items A,B,C..they can pack them all 3 into 1 box

But, If they have Items- A,B,D,they will have to use 2 boxes..1st box for A,B and 2nd Box for Item D.

Any ideas, how to handle this business scenario in Non WMS Organization.