The whole system sounds like a "class change" mechanic from various videogames. I have always loved such mechanics, so I am looking forward to this.
For those of you who don't know what I am talking about, and to clarify, here are some examples from the videogame Fire Emblem: The Sacred Stones.
A basic axe-using soldier is called a Fighter. By building up to level 20, he can class change into a level 1 Warrior, who has all the power of a level 20 Fighter, but more power added onto that, and the ability to use bows. Alternatively, the Fighter can class change into a Hero, who has fewer hitpoints and less attack power than the Warrior, and isn't able to use bows, but is faster and can use swords.
Similarly, a heavily armored infantry unit called the Knight can class change into either a Great Knight (a powerful heavy cavalry unit), or a General (still armored infantry, but has the ability to deflect any attack). Either way, the former Knight (who could only use lances), can now use axes and swords.
Versatile Cavaliers, the basic cavalry unit, can class change into either Great Knights (the same class that Knights can change into), or more mobile Paladins.
A basic Mage (who can only use Anima Magic) can class change into either a Sage or a Mage Knight. Sages can use Light Magic, but Mage Knights are mounted units. Either class change would let the former Mage use healing staves.
I really expect the Paragon Path/Epic Destiny system to be similar. They are different options that add to the basic abilities of a class in different ways, without reducing any of the class's original abilities.