Brother MacLaren said:
By taking away the possibility of delayed gratification (sub-par feats now in exchange for superior PrC abilities later), you are taking an option away from the players. A class like the DD shows a steeper power curve (if you are looking at core only). The character is somewhat weaker than a core fighter from levels 1-7, because of his sub-optimal feats, but somewhat better at levels 8 and up. If that's what a player wanted, this option was there for them. Are you saying that shouldn't be an option anymore?
I can't speek for the OP, bu from my view:
1) It's problematic if you want to maintain game balance. Once you don't start at lower levels, people will have a tendency to pick the classes that are stronger at high levels. It's not guaranteed (not everyone is a power gamer first

, but it's still a problem.
2) How important is "delayed gratification" really in an on-going campaign. The level system inherently will always make you bad at start and good at the end. Do you really notice that you were consistently worse then "stable gratification" character and now are consistently better then him? Or won't you focus more on the aspect that at 1st level, an Ogre was a terrifying monster and at 20th level, you could wade through hordes of them?
3) You're not playing alone. If your character sucked at the early levels, that might mean that your party mates got to shine more, but it also means that you were not pulling your own weight and they had to work harder. At higher levels, your character begins to overshadow them, taking more spotlight, and they look back "we had to work so hard to get here, and now (only) he is doing all the cool stuff!".
Now, this is obviously exaggerated, but the core is that your choice for a certain character class can or probably will affect the other player negatively, and that is not a good design. You might be allowed to make stupid decision in-character (attacking the wrong target, inciting a fight where talk would have been safer, not stopping to heal a comrade, heck, even casting fireball in between your party and your enemies), but if possible, the mechanics shouldn't force this on you.