Aperture: change image verson naming format?

The "Edit..."option at the bottom of the "Version Name Format" list. Use that to create your own renaming rules. You want to add a new preset with the rule "[Version Name] (2)". Do not tick/check "Apply to Master Files" when you rename and you should have a version with the original file name and a version name with (2) appended.

If that makes sense!