I woud contact App Store Connect and ask this question. However, I don't think that this is possible. If this is the case, one suggestion is to that you may need to revise the app to have Group 2 subscribers no longer be able to renew their subscriptions - create the new items in group1 and advise current group 2 subscribers to buy into the new subscriptions when their current subsriptions end. The app can detect when the G2 subscriptions are about to end and alert the user.
Maybe others on this forum can think of alternative solutions.
rich kubota - email@example.com
developer technical support CoreOS/Hardware/MFI
Thank you for your reply.
I'm sending the question to the app store connect. If I can solve this problem I will update again.
Could you create two new subscriptions, add them to one of the two groups, say G1, and then ask people in G2 to switch to the equivalent subscription in G1?