The problem is, players do not want to do this. There are several issues with this plan.
- First off, not everyone has all of the content.
- Second, some of those who have it, do not enjoy it.
- Third, from what I have seen, most people want to perform heroic TR ASAP, without having to delve into Epic levels; the latter sagas are Lv 24 range on heroic I believe, which forces people to perform a significant dedication to Epic levels.
- Fourth, it narrows what you can play, rather then encourages a variety. You can only get credit from saga quests, and only once per saga; if there is a quest you want to play repeatedly, you have to slog through other quests before you can get credit for the one you like again.
- Fifth, it removes an existing, functional system in order to replace it with a longer grind time unless you have "optimal" content. There are plenty of partial or half-functioning systems that players would absolutely love see improved upon, rather then distressing an existing, working one.