distant peak
Basically many "High Expansion, Low Penetration" bullets have been not very useful ever since the Animal Scoring 2.0 update came out, and made "High Penetration" bullets even better than what they were before since now it is only necessary to hit a single vital organ to pass one of the harvest check criteria.
And because "High Expansion" bullets have so much less penetration, it makes it almost impossible to shoot animals from the front since the bullet will completely fail to penetrate into the lungs/heart.
So one suggestion would be to improve the penetration of the "High Expansion" bullets, in order to make them more useful and more practical. How much the penetration of "High Expansion" bullets should/could be improved would need to be analyzed on each case, and I still believe that "High Penetration" bullets should still retain a noticeable penetration advantage over the "High Expansion" bullets.
So my idea would be to generally make "High Expansion" bullets at least (barely) capable of getting "Double Lungs" (but only from very good shots), and make "High Penetration" bullets easily capable of achieving double lungs (specially from lesser than ideal angles)