He's a very good project to have on a team like this. Obviously he needs lots of time and patience and this is one of the few teams in the league looking at such a long rebuilding job that they can give him both patience and playing time. I don't think it's a coincidence that Charlotte has chosen such young players. It helps the rebuilding process by not creating artificially high win totals in the first couple years, so that the team keeps racking up really high draft picks. Then, when the stars are on the roster, supporting players like Biyombo will be ready to fulfill their very specific role. Suddenly a player that seemed limited because he couldn't carry a team on his back to thirty wins, seems like a wonderful player because he fits well in a team with stars and does a great job at the few things the team desperately needs him to do (in this case, rebound and defend the paint).
That's the theory and I think it's a sound one. However, draft history is littered with foreign big-men ultimately unable to make the transition to the NBA. Biyombo could easily be one of those casualties; I don't think anyone can say with certainty at this point, which way the experiment will go. But all you can ask of a front office is that they have a good plan and a good process. Every front office makes draft picks that don't pan out. Look at OKC and Jeff Green, Miami and Michael Beasley, etc. But if the plan and process is sound, things will progress.