[Jamz]

It depends on how far you take it. Really, it would just be another "attribute" in the XML stating what "Level" said feat, option, class, etc it was chosen.

It would require another option in HL to "Lock" the character as well, that is, not allow you to add 5 class levels at once and force you to add one level and all feats/etc then hit the "level up" button to lock it all in.

Again, it would be nice but it personally would be lower on my wish list. You learn to just create a level 12 version (or 20) of your character first and save it in the same portfolio and just reference it when needed.