The popularity of semi-western and lots of topspin is because it's easier to keep the ball in play. If you use an eastern grip and hit the ball hard and flatter, it will take much longer to reach a similar level of consistency. The problems will be magnified when you play someone a little better than you.
Delpo hits flatter than most as do many WTA players. How do they do it so successfully? Thousands of hours of practice.