I don't think Lydon's ideal position is the 3. On defense, of course, the 3 and 4 are interchangable, but on offense, Lydon is far, far more valuable as a 4 or even a 5. In today's world, there are really 3 positions on offense, Bigs, Wings, and Point Guards. If Lydon is a PF (big), he can force other rim-protecting bigs to leave the paint and cover him at the 3 point arc where he can drive by them or pass into the middle where there's one less rim protector. As a SF (wing) his strengths would be offensive rebounding and bullying his smaller man in the post. Given his current skill set (and the makeup of the team), I want the former advantages not the latter.
Tl;dr Lydon is more valuable as a stretch 4 than as an oversize 3.
Also, Lydon's not 6'8. He was 6'8.75 without shoes last year. In shoes (which is how everyone compares heights) he's probably closer to 6'10. Also, he's got a 7 foot wingspan which makes him even taller.