Understood!
Well, currently there is no way to do that the way you want. By changing templates mid-game, because they are added by note tags and that note tag is read on a specific place on the code.
For now, I believe the way I shown to you is the way to go. Honestly, I think it is more clean too and easy to maintain. With multiple templates, when you want to change something you would need to open each one, do a lot of clicks until you get what you want to change them.
With what I have shown to you, you can change "templates" mid game using a variable as personality. Or even better, creating a custom property on your actors:
$gameActors.actor(id).personality = "Brave"
That way instead of using this :
const personality = $gameVariables.value(ID)
you can use this :
this.personality