Jack99
Adventurer
What I'm thinking is more about an organic method of character development. At level 1 you decide to be a fighter. You have your character backstory, all that jazz, but you don't have a build in mind. Somewhere around level 6 your character has a fight in a temple of Tymora and all his allies are unconscious, he is the only one left against a servant of bane who the party is after. He has 1 hp and he manages to get lucky and pulls of a critical hit, dropping the servant of bane from half health to the ground. He attributes it to Tymora and takes up her worship and wants to become a cleric of Tymora and focus on that entirely as opposed to his training as a fighter. In 3.x the next time he leveled up he would take a level of cleric and continue on that way, possibly taking a prestige class eventually that fit it but probably never taking a level of fighter again. He views himself as a cleric now, even though he still has his fighter training.
Is there any equivalent to that type of mid-game choice available in 4e? Not retroactive, where he gives up his fighter levels and boom, he's a level 6 cleric, but where he could put his fighter training aside-while retaining it, but focus on becoming a cleric instead.
That's exactly how it works in 4e. In your example, the fighter would retrain his level 6 feat and grab a multiclass cleric feat (and thus a power) at level 7, then grab another cleric multiclass feat at 8 (and another power) before finally getting his 3rd multiclass feat at level 10 (and switch yet another power). Then at 11, he could paragon multiclass to cleric, giving him a cleric at-will power and go from there. He would effectively become more and more cleric-like as levels go up.