Can we enable future segment as Intercompany Segment ?

Summary:

We currently do not have intercompany segment in our chart of accounts, and have been live for over 2 years. We now need intercompany segment.

Our company segment is 2 characters, and our future segment is 6 characters.

Question 1: is it possible to enable the future segment as intercompany, and still use the intercompany functionality even though the characters dont match?

Question 2: What is the impact of these changes on the previous and future transactions if it is available to be done?

Thanks and any insight much appreciated, if anybody has run into this issue.