There is a reoccurring issue from using original game saves and not a mod save called a
KeyError U 'charactername' error. But all you need to do to fix this issue is go to the MC's room and click on the duffel bag. Then select the Rename Character option and the last option in the menu is
All Names Reset to Default. Click on that and it will fix that issue. You can then use the options above that one to rename any characters you had custom names for.
That is the biggest issue I run into with old saves. Other than that, most old saves work just fine.
There are rare occasions where an abnormal error happens and you do have to do a brand new save, but that has been few and far between in my personal experience.
Thanks for your interest in trying out the mod.