Lescott was a quality player, no doubt about it but we also went though spells with him the side where we couldn't defend for toffee. The only time when he ever looked the part was alongside Jags in there last spell together, before that he was always more effective at left back. And he was very impressive at left back, to be fair to him, a little unorthodox but effective in both areas of the pitch.
Heitinga have been very consistent in both central positions, he's shown he could comfortably do a job in either position. You can count the amount of mistakes he's made on one hand, and every defender in world football will make the odd mistake here and there, even the best. Yes we've conceded too many goals but very few have come from Heitinga and you defend as a team, it isn't just about your centre backs.
As for a potential Jagielka-Heitinga partnership, there lack of height may be a problem, we'll have to wait and see on that one but the main attributes for defending is concentration, consistency and positional sense and both players have that in abundance. Add Jagielka's athleticism and Heitinga's intelligence and distribution and they've both got alot going for them. And our none of our bigger defenders are exactly dominant in the air, Yobo, Lescott and Distin certainly aren't.
Heitinga in midfield is another option, he has the defensive qualities and quality of distribution to make it happen but I really don't want to see a midfield of Heitinga, Arteta and Fellaini. One of them will have to do a job further forward and whilst Arteta and Fellaini can they are at there best in the middle of the park. Heitinga/Fellaini, Arteta and one of Cahill/Pienaar/Bilyaletdinov would be much more balanced.