Problem with my extraction

1) Already one LO extraction say it for SD is up and running live with all the process chain and so.. If i get a requirement to add few more field to tis ... how will you do it with minimal impact on prod data which is already live

2) Alreday VAHDR is up and running live... how to active VAITM with minimal effect without impacting VAHDR..

My idea for this was create a replica of the same with additional field make already existing process chain inactive and make new one active and schedule it

If any better suggestion to approach this problem please let me know it. I am waiting for your response. Thanks in advance