Awesome! Thanks for the explanation. I get it. I'm not sure I'd do it, myself (I'd be more likely to tell the player "you can bring in a character of any level from 1st to X, your choice"), but I get it.
I really agree with you about the organic sense of growth, and the importance of rank to players who have worked their way up. The "young hunters go out with the veterans" thing is fascinating.
The one time we did this, we had a 1st lvl PC apprenticed to one particular PC in the party, technically as a punishment and to teach him some responsibility. It worked quite well because the player had insisted on being 1st level. I did have to pull a punch or two, though, letting other heroes give the apprentice full cover vs fireballs by throwing themselves on the low-lvl PC (a ruling that no one complained about, even if it felt a little weird to me.)