Firstly, a distinction should be made between some things.
What Trez himself is capable of, how Lippi wants him to play and how we expect him to play are probably all different. Those who know the Frenchman will understand that he's fully capable of more than just being a 'box' player. If the coach's expectation is different, what's the point of buying another guy who could just as well end up the same?
DV vs Chevanton though, is quite another matter. It isn't apples vs oranges for one but a direct comparison between very similar players in the same function. Even at 23, he's already a seasoned Serie A campaigner who's at least as accomplished as DV is. Ability-wise, he's wonderfully complete. Perhaps most importantly, he displays a work ethic that's perfectly suited to Juve.
Assuming Chevanton delivers (unfortunately, quite a big IF), his impact would be HUGE. His physique shouldn't be too much of a concern since if it didn't hamper Nedved (different roles aside, their physique and styles are remarkably similar), it shouldn't hamper him either.
I am quite a fan of the little Uruguayan. Lecce will sell but not to anyone else in the Serie A, I hope.