Hi Chuck,
Please take a look at this DocOps article on how to add a new Environment:
Add an Environment to an Existing Inventory Structure - CA Endevor® SCM - 18.0 - CA Technologies Documentation
Do you plan to use the first stage in PROD for like Emergency Fixes or is it going to be an empty / null stage?
Do you plan to use both stages of the new ACPT Environment?
If you only plan to use 1 stage, it must be Stage 2 and in the C1DEFLTS you would specify the Stage 2 entries and specify ENTRYSTG#=2.
You are correct, you can just move the MCF file from Stage 1 of PROD to Stage 2 of ACPT in the C1DEFLTS and not create new ones.
If you plan to use both stages, you will need to create a new MCF for Stage 1 and specify it in the C1DEFLTS.
You can use either batch jobs or Clone the Systems, Subsystems, and Types using the ISPF panels.
Please review the DocOps article and let me know if you have any questions.
June