Which all still makes the case for creating complete age groups because not everyone creates their CAS sims first in BodyShop. This is tedious, but not hard. Just use the saved adult sims, age transition them, save them again, and extract the info in the same manner suggested in the tutorial.
Tedious, yes... sigh... I also came to that conclusion. I think that only a few changes in a new face will make that face look older. Applying the same kind of changes to all the new templates will probably do the job. Same for the teens. I agree with Motoki that it is not so important to change the children.
EDIT: I'm also not sure about the following situation. If a CAS-created playable sim is bound to the templates, and then the changed templates are introduced, will the sim in question then use the new template when age transitioning -- in essense using the deviation of clicks used to create its uniqueness and then applying those deviations to the next age template it transitions to? The bad news would be that if its true, then even replacing all the templates in every age group could still mean radical face changes for any CAS-created sim that was made prior to introducing the new templates. The only neighborhoods that would be immune would be those started from scratch with the new templates and those pre-played neighborhoods where all CAS sims were created from BodyShop files.
This afternoon I'll do some experimentation on this. I consider that the game acts like this: amArchHeart + tweaking becomes emArchHeart + same tweaking when growing old.
What I hope: New amArchHeart + tweaking becomes New emArchHeart + tweaking.
What I fear: New amArchHeart + tweaking becomes original emArchHeart + tweaking.
It all depends on how Maxis has bound the faces to the templates.