Significant routing and resource group changes

Looking for some advice here. We have three sets of two machines, configured as such.
Resources 1 and 2 are in resource group A, Resources 3 and 4 are in resource group B, and resources 5 and 6 are in resource group C.

We want to separate the resources from the group, so all six machines will have their own resource groups.

Currently, our routings call out Resource Group A, and certain ops will specify the resource within the group.

How can we reconstruct the resource groups in a manner that will not compromise the integrity of the existing jobs that are in process? We can edit the routings themselves pretty quickly on the methods, but my concern is that we will have plans that reflect the new resource group construction, but the existing jobs will not.

Looking for a creative solution. To answer anyone’s question about why we are doing this, we are setting up a cell utilizing existing equipment in the building. That is what is forcing me to be creative in separating the resources/resource groups.

Thanks, folks.