natural account changes

Hi

this year our company decide to change our natural accounts list, what should we do in this case:
 
1: create a new value set with the new accounts.
2: use the future use segment, and affect the natural account flexfield qualifier to this segment.
the first suggestion: can we have all old data before changes are made.
the second seggestion: what about old data can all reports have the new and old data to compare them.

Best regards