If they're gonna be good, then they're gonna be good and no C class fighter with 30, 40, 50 fights would beat them. There's been much worse that have been overcome.
These guys fought A-/B+ fighters early in their careers, and they have turned out fine:
A 17 fight, young, green Floyd fighting the 130 Lineal champion who had 39 fights, only one loss, Genaro Hernandez.
A 20-0 Andre Ward, beating the Super 6 Tourney favorite Mikkel Kessler who had 43 fights and 1 loss.
De La Hoya at 16-0, 17-0, 18-0, 19-0 fought Molina[36-3], Ruelas[43-1], Hernandez[32-0], and Leija[30-1]. All top 10 fighters at LW at the time, and Oscar was only 22/23 years old.
A 18-fight Nonito Donaire fighting an undefeated, near 30-fight favorite Vic Darchinyan.
Hernandez, Kessler, Darcchinyan, Molina, Ruelas, Hernandez, Leija>PDL, Abregu, even the Vic that Donaire fought>the Vic that Del Valle fought.
Like I said, if you're going to be good, then you're going to be good. Stop with the stupid "being fed to lion's" excuse. If they're losing to a 40 year old Vic and Carlos Abregu, then they're not going to be that good regardless of how much time you give them.